16020 - 07/71
/tXEAKh,
METHODS FOR CHEMICAL ANALYSIS
OF
WATER AND WASTES
1971
ENVIRONMENTAL PROTECTION AGENCY
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METHODS FOR CHEMICAL ANALYSIS
OF
WATER AND WASTES
1971
ENVIRONMENTAL PROTECTION AGENCY
National Environmental Research Center
Analytical Quality Control Laboratory
Cincinnati, Ohio 45268
-------
DISCLAIMER
Mention of trade names or commercial
products does not constitute endorse-
ment by the Water Quality Office or
the Environmental Protection Agency.
For sale by the Superintendent of Documents, U.S. Government Printing Office
Washington, D.C. 20402- Price $3
Stock Number 5501-0067
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PREFACE
This manual describes the analytical procedures selected for use in
Water Quality Office laboratories for the chemical analysis of water and
waste samples. The methods were chosen by a committee of senior chemists
from within the Office, using Standard Methods for the Examination of
Water and Wastewater, 13th Edition (1971) and ASTM Standards, Part 23,
Water; Atmospheric Analysis (1970), and current water pollution control
literature as basic references. When necessary, methods derived from
these sources have been modified or replaced to more adequately meet the
needs of the Office.
In order to provide reliable water quality and waste constituent
data for use by the Office, these procedures will be used in all Office
laboratories except under very unusual circumstances. Other agencies and
individuals are encouraged to use these methods, in the interest of uni-
formity throughout the water pollution control effort.
David D. Dominick
Acting Commissioner
Water Quality
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TABLE OF CONTENTS
Page
Introduction ix
Sample Preservation 1
Acidity (Electrometric Titration, pH 8.3) 5
Alkalinity
Manual (Electrometric Titration, pH 4.5) g
Automated (Methyl Orange) g
Arsenic (Silver Diethyldithiocarbamate) 13
Biochemical Oxygen Demand (Winkler-Azide or DO Probe) 15
Chemical Oxygen Demand
Routine Levels (Dichromate Reflux-0.25N) 17
Low Level (Dichromate Reflux-0.025N) 19
Saline Waters (Chloride Correction) 24
Chloride
Manual (Mercuric Nitrate Titration) 29
Automated (Ferricyanide) 31
Chlorine Requirement . 36
Color (Platinum-Cob alt Visual) 38
Cyanide (Silver Nitrate Titration or Pyridine-Pyrazalone) 41
Dissolved Oxygen
Manual (Winkler-Azide) 53
Probe (Ion Selective Electrode) 60
Fluoride
Manual (SPADNS, with Distillation) 64
Automated (Complexone) 66
Probe (Ion Selective Electrode) 72
Hardness
Manual (EDTA Titration) 76
Automated (Calmagite) 78
Calculation (Ca + Mg by Atomic Absorption) 83
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TABLE OF CONTENTS (Contd.)
Page
Metals (Atomic Absorption Methods)
Aluminum [[[ gg
Arseni c [[[ 99
Cadmium [[[ JQI
Calcium [[[ 102
Chromium
c°PPer [[[ 106
Iron [[[ 108
Lead [[[ 110
Magnesium [[[ , •, 2
Manganese [[[ •, -, »
Potassium [[[
Silver [[[
Sodium [[[
zinc [[[ 120
Mercury (Flameless AA) ^ ..............................................
Methylene Blue Active Substances (Methylene Blue) .....................
Nitrogen
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TABLE OF CONTENTS (Contd.)
Page
Nitrilotriacetic Acid (NTA)
Manual (Zinc-Zincon) 205
Automated (Zinc-Zincon) 209
Oil and Grease (Hexane Soxhlet Extraction) 217
Organic Carbon (Instrumental) 221
pH (Electrometric) 230
Phenolics (4-Aminoantipyrine) 232
Phosphorus, All Forms
Manual (Single Reagent) 235
Automated (Single Reagent) 246
Automated (Stannous Chloride) 259
Selenium (Diaminobenzidine) 271
Silica (Molybdate) 273
Solids
Filterable (Glass Fiber, 180°C) 275
Non-Filterable (Glass Fiber, 103-105°C) 278
Total (Gravimetric, 105°C) 280
Volatile (Gravimetric, 550°C) 282
Specific Conductance (Wheatstone Bridge) 284
Sulfate
Manual (Turbidimetric) 286
Automated (Barium Chloranilate) 288
Sulfide (lodometric) 294
Temperature (Mercury, Dial, or Thermistor) 296
Threshold Odor (Consistent Series) 297
Turbidity (Instrumental) 308
Vll
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INTRODUCTION
This 1971 edition of "Methods for Chemical Analysis of Water and Wastes"
describes chemical analytical procedures to be used in Water Quality Office
(WQO) laboratories. The methods were chosen through the combined efforts of
the Regional Analytical Quality Control CAQC) Coordinators, Laboratory Quality
Control Officers, and other senior chemists in both federal and state labora-
tories. Method selection was based on the following criteria:
(1) The method should measure the desired constituent with precision and
accuracy sufficient to meet the data needs of WQO in the presence of
i
the interferences normally encountered in polluted waters.
(2) The procedures should utilize the equipment and skills normally avail-
able in the typical water pollution control laboratory.
C3) The selected methods are in use in many laboratories or have been suf-
ficiently tested to establish their validity.
[4) The methods should be sufficiently rapid to permit routine use for the
examination of a large number of samples.
Except where noted under "Scope and Application" for each constituent, the
methods can be used for the measurement of the indicated constituent in both
water and wastewaters and in both saline and fresh water samples.
Instrumental methods have been selected in preference to manual procedures
because of the improved speed, precision, and accuracy. Procedures for the
Technicon AutoAnalyzer have been included for laboratories having this equip-
ment available.
Precision and accuracy statements have been derived from inter-laboratory
studies conducted by the Methods and Performance Activity, Analytical Qual-
ity Control Laboratory, WQO; the American Society for Testing Materials; or
the Analytical Reference Service of the Public Health Service, DHEW.
ix
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Specific instructions for the handling and preservation of samples cannot be
given because of the wide variability in types of samples and local sampling
situations. However, certain general principles should be followed. Wherever
possible, the sampling program should be designed to provide for the shortest
possible interval between sample collection and analysis. Positive steps
should be taken to maintain both the concentration and the physical state of
the constituents to be measured. Where both total and dissolved concentrations
are to be determined, the dissolved concentration is the amount present after
filtration through a 0.45 membrane filter. When the dissolved concentration
is to be determined, filtration should be carried out as soon as possible after
collection of the sample, preferably in the field. Where field filtration is
not practical, the sample should be filtered as soon as it is received in the
laboratory.
In situations where the interval between sample collection and analysis is long
enough to produce significant changes in either the concentration or the physical
state of the constituent to be measured, the preservatives listed in Table II
are recommended.
Although every effort has been made to select methods which are applicable to
the widest range of sample types, significant interferences may be encountered in
certain isolated samples. In these situations, the analyst should define the
nature of the interference with the method herein and bring this information to
the attention of the Analytical Quality Control Laboratory through the appropriate
Regional AQC Coordinator. Recommendations for alternative procedures will be made
and modification of the method will be developed to overcome the interferences.
x
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Regional Analytical Quality Control Coordinators
Warren H. Oldaker, AQC Coordinator
Environmental Protection Agency, Region I
John F. Kennedy Building, Room 2303
Boston, Massachusetts 02203
Francis T. Brezenski, AQC Coordinator
Environmental Protection Agency, Region II
Edison Water Quality Laboratory
Edison, New Jersey 08817
i
Charles Jones, Jr., AQC Coordinator
Environmental Protection Agency, Region III
Custom House, Room 1004
Second § Chestnut Streets
Philadelphia, Pennsylvania 19106
James H. Finger, AQC Coordinator
Environmental Protection Agency, Region IV
Southeast Water Laboratory
College Station Road
Athens, Georgia 30601
LeRoy E. Scarce, AQC Coordinator
Environmental Protection Agency, Region V
Illinois District Office
1819 West Pershing Road
Chicago, Illinois 60609
Bobby G. Benefield, AQC Coordinator
Environmental Protection Agency, Region VI
Kerr Water Research Center
P.O. Box 1198
Ada, Oklahoma 74820
Dr. Harold G. Brown, AQC Coordinator
Environmental Protection Agency, Region VII
911 Walnut Street, Room 702
Kansas City, Missouri 64106
John R. Tilstra, AQC Coordinator
Environmental Protection Agency, Region VIII
Suite 900, Lincoln Tower Building
1860 Lincoln Street
Denver, Colorado 80203
Donald B. Mausshardt, AQC Coordinator
Environmental Protection Agency, Region IX
Phelan Building, 760 Market Street
San Francisco, California 94102
Daniel F. Krawczyk, AQC Coordinator
Environmental Protection Agency, Region X
Pacific Northwest Water Laboratory
200 South 35th Street
Corvallis, Oregon 97330
XI
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SAMPLE PRESERVATION
Complete and unequivocal preservation of samples, either domestic sewage,
industrial wastes or natural waters, is a practical impossibility. Regard-
less of the nature of the sample, complete stability for every constituent
can never be achieved. At best, preservation techniques can only retard the
chemical and biological changes that inevitably continue after the sample is
removed from the parent source.
The changes that take place in a sample are either chemical or biological. In
the former case, certain changes occur in the chemical structure of the con-
stituents that are a function of physical conditions. Metal cations may
precipitate as hydroxides or form complexes with other constituents; cations
or anions may change valence states under certain reducing or oxidizing con-
ditions; other constituents may dissolve or volatilize with the passage of
time. Metal cations may also adsorb onto surfaces (glass, plastic, quartz,
etc.), such as, iron and lead. Biological changes taking place in a sample may
change the state of an element or a radical to a different state. Soluble con-
stituents may be converted to organically bound material in cell structures, or
cell lysis may result in release of cellular materials into solution. The
well known nitrogen and phosphorus cycles are examples of biological influence
on sample composition.
Methods of preservation are relatively limited and are intended generally to
(1) retard biological action, (2) retard hydrolysis of chemical compounds and
complexes and (3) reduce volatility of constituents.
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Preservation methods are generally limited to pH control, chemical addi-
tion, refrigeration, and freezing. Table 1 shows the various preservatives
that may be used to retard changes in samples.
Table 1
Preservative
HgCl,
Acid (HN03)
Acid (H2S04)
Alkali (NaOH)
Refrigeration or
freezing
Action
Bacterial Inhibitor
Metals solvent, prevents
precipitation
Bacterial Inhibitor
Salt formation with
organic bases
Salt formation with
volatile compounds
Bacterial Inhibitor
Applicable to:
Nitrogen forms,
Phosphorus forms
Metals
Organic samples (COD,
oil § grease, organic
carbon, etc.)
Ammonia, amines
Cyanides, organic
acids
Acidity - alkalinity,
organic materials,
BOD, color, odor,
organic P, organic N,
carbon, etc., biological
organisms (coliform, etc.)
In summary, refrigeration at temperatures near freezing or below is the best
preservation technique available, but is not applicable to all types of
samples.
The recommended choice of preservatives for various constituents is given in
Table 2. These choices are based on the accompanying references and oh infor-
mation supplied by various Regional Analytical Quality Control Coordinators.
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Table 2 - Sample Preservation
Parameter
Acidity-Alkalinity
Biochemical Oxygen Demand
Calcium
Chemical Oxygen Demand
Chloride
Color
Cyanide
Dissolved Oxygen
Fluoride
Hardness
Metals, Total
Metals, Dissolved
Nitrogen, Ammonia
Nitrogen, Kjeldahl
\
Nitrogen, Nitrate-Nitrite
Oil and Grease
Organic Carbon
pH
Phenolics
Phosphorus
Preservative
Refrigeration at 4°C
Refrigeration at 4°C
None required
2 ml H2S04 per liter
None required
Refrigeration at 4°C
NaOH to pH 10
Determine on site
None required
None required
5 ml HNO_ per liter
O
Maximum
Holding Period
24 hours
6 hours
7 days
7 days
7 days
24 hours
24 hours
No holding
7 days
7 days
6 months
Filtrate: 3 ml 1:1 HNO per liter 6 months
J
40 mg HgCl * per liter - 4°C
40 mg HgCl * per liter - 4°C
40 mg HgCl2* per liter - 4°C
2 ml H2S04 per liter - 4°C
2 ml H2SO. per liter (pH 2)
Determine on site
1.0 g CuS04/l + H3P04 to
pH 4.0 - 4°C
40 mg HgCl * per liter - 4°C
7 days
Unstable
7 days
24 hours
7 days
No holding
24 hours
7 days
*Disposal of mercury-containing samples is a recognized problem; research
investigations are under way to replace it as a preservative.
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Table 2 - Sample Preservation
(Continued)
Maximum
Parameter Preservative Holding Period
Solids None available 7 days
Specific Conductance None required 7 days
Sulfate Refrigeration at 4°C 7 days
Sulfide 2 ml Zn acetate per liter 7 days
Threshold Odor Refrigeration at 4°C 24 hours
Turbidity None available 7 days
References:
Jenkins, David, "A Study of Methods Suitable for the Analysis and Pre-
servation of Phosphorus Forms in an Estuarine Environment." Report
for the Central Pacific River Basins Project, Southwest Region,
FWPCA (1965).
Jenkins, David, "A Study of Method for the Analysis and Preservation
of Nitrogen Forms in an Estuarine Environment." Report for the
Central Pacific River Basins Project, Southwest Region, FWPCA (1965).
Howe, L. H. and Holley, C. W. "Comparisons of Mercury (II) Chloride
and Sulfuric Acid as Preservatives for Nitrogen Forms in Water
Samples." Env. Sci. § Tech. 3:478 (1969).
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ACIDITY
STORE! NO. 00455
1. Scope and Application
1.1 The method recommended is identical to the procedure described in
ASTM Standards, Part 23, pp 155-158, except that the sample is
titrated to a final pH of 8.3 and results reported as mg/1 CaCO .
1.2 This method is not applicable to analysis of acid samples from mine
drainage. It is the decision of the AQC staff to delay the method
selection for measurement of acidity in acid mine drainage samples
until such time that a more comprehensive review of the problem can
be made.
1.3 Methods for analysis of mine drainage samples for all constituents
contributing to acidity of such samples may be selected at the option
of the respective laboratory directors.
2. Calculation
2.1 Acidity is reported as calcium carbonate (CaCO,) according to the
following formula:
A -j-* /i r ™ A X N X 50,000
Acidity as mg/1 CaC03 = ml sampi;
where:
A = ml of base used for titration
N = normality of base
3. Precision and Accuracy
3.1 Forty analysts in seventeen laboratories analyzed synthetic water
samples containing increments of bicarbonate with the following results:
Increment as
Acidity
mg/1, CaC03
20
21
Precision as
Standard Deviation
mg/ liter, CaCO,
1.79
1.73
Accuracy as
Bias,
+2.77
+0.52
Bias,
mg/liter,
+ .55
+ .11
CaCO
(FWPCA Method Study 1, Mineral and Physical Analyses)
5
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ALKALINITY
STORET Number: 00410
1. Scope and Application
1.1 This method is applicable to drinking waters and surface waters,
domestic and industrial wastes, and saline waters.
1.2 The method is suitable for all concentration ranges of alkalinity;
however, appropriate aliquots should be used to avoid a titration
volume greater than 50 ml.
1.3 Automated titrimetric analysis is equivalent.
2. Summary of Method
2.1 An unaltered sample is titrated to an electrometrically determined
end point of pH 4.5. The sample must not be filtered, diluted,
concentrated, or altered in any way.
3. Comments
3.1 The sample must be analyzed as soon as practical; preferably,
within a few hours. Do not open sample bottle before analyses.
3.2 Substances, such as salts of weak organic and inorganic acids
present in large amounts, may cause interference in the electro-
metric pH measurements.
3.3 Oil and greases, by coating the pH electrode, may also interfere,
causing sluggish response.
4. Precision and Accuracy
4.1 Forty analysts in seventeen laboratories analyzed synthetic
water samples containing increments of bicarbonate, with the
following results:
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(Alkalinity)
Increment as
Alkalinity
rag/ liter, CaCO
8
9
113
119
Precision as
Standard Deviation
mg/liter, CaCO_
J
1.27
1.14
5.28
5.36
Accuracy
Bias,
%
+10.61
+22.29
- 8.19
- 7.42
as
Bias,
mg/liter, CaCO
+0.85
+2.0
-9.3
-8.8
(FWPCA Method Study 1, Mineral and Physical Analyses)
4.2 In a single laboratory (AQC), using surface water samples at an
average concentration of 122 mg CaCO,/l, the standard deviation
was ± 3.
5. Reference
5.1 The procedure to be used for this determination is found in:
Standard Methods for the Examination of Water and Wastewater,
13th Edition, p. 52, Method 102 (1971).
ASTM Standards, Part 23, Water; Atmospheric Analysis, p. 154,
Method D-1067 (1970).
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TOTAL ALKALINITY
(Automated Methyl Orange Method)
STORET NO. 00410
1. Scope and Application
1.1 This automated method is applicable to surface and saline waters. The
applicable range is 10 to 200 mg/1 as CaCO,.
2. Summary of Method
2.1 Methyl orange is used as the indicator in this method because its pH
range is in the same range as the equivalence point for total alka-
linity, and it has a distinct color change that can be easily measured.
The methyl orange is dissolved in a weak buffer at a pH of 3.1, just
below the equivalence point, so that any addition of alkalinity causes
a loss of color directly proportional to the amount of alkalinity.
3. Sample Handling and Preservation
3.1 Sample should be refrigerated at 4°C and run as soon as practical.
4. Interferences
4.1 No significant interferences.
5. Apparatus
5.1 Technicon AutoAnalyzer consisting of:
5.1.1 Sampler I.
5.1.2 Manifold.
5.1.3 Proportioning pump.
5.1.4 Colorimeter equipped with 15 mm tubular flow cell and 550 ™n
filters.
5.1.5 Recorder equipped with range expander.
6. Reagents
6.1 Methyl Orange: Dissolve 0.125 g of methyl orange in 1 liter of
distilled water.
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(Total Alkalinity)
6.2 pH 3.1 Buffer: Dissolve 5.1047 g of potassium acid phthalate in
distilled water and add 87.6 ml 0.1 N HC1 and dilute to 1 liter.
Stable for one week.
6.3 Methyl Orange-Buffered Indicator: Add 1.0 liter of pH 3.1 buffer to
200 ml methyl orange solution and mix well. Stable for 24 hours.
:6.4 Stock Solution: Dissolve 1.060 g of anhydrous sodium carbonate
(oven-dried at 140°C for 1 hour) in distilled water and dilute to
1.0 liter. 1.0 ml = 1.00 mg CaCO .
J
6.4.1 Prepare a series of standards by diluting suitable volumes of
stock solution to 100.0 ml with distilled water. The following
dilutions are suggested:
ml of Stock „ /n _, „_.
Solution Conc.,mg/l as CaC05
1.0 10
2.0 20
4.0 40
6.0 60
8.0 80
10.0 100
18.0 180
20.0 200
7. Procedure
7.1 No advance sample preparation is required. Set up manifold as shown
in Figure 1.
7.2 Allow both colorimeter and recorder to warm up for 30 minutes. Run
a baseline with all reagents, feeding distilled water through the
sample line. Adjust dark current and operative opening on colorimeter
to obtain stable baseline.
7.3 Place distilled water wash tubes in alternate openings on sampler and
set sample timing at 2.0 minutes.
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(Total Alkalinity)
7.4 Place working standards in sampler in order of decreasing concentration.
Complete filling of sampler tray with unknown samples.
7.5 Switch sample line from distilled water to sampler and begin analysis.
8. Calculation
8.1 Prepare standard curve by plotting peak heights of processed standards
against known concentrations. Compute concentration of samples by
comparing sample peak heights with standard curve.
9. Precision and Accuracy
9.1 In a single laboratory (AQC), using surface water samples at concen-
trations of 15, 57, 154, and 193 mg/1 as CaCO,, the standard deviation
«J
was ±0.5.
9.2 In a single laboratory (AQC), using surface water samples at concen-
trations of 31 and 149 mg/1 as CaCO_, recoveries were 100% and 99%,
respectively.
References
1. Technicon AutoAnalyzer Methodology, Bulletin 1261, Technicon Controls, Inc.,
Chauncey, N.Y. (1961).
2. Standard Methods for the Examination of Water and Wastewater, 13th Edition,
p. 52, Method 102 (1971).
10
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ml / min ^5od^
LARGE MIXING COILS /
00000000 00000000 . /
f
s==s 1/2 DELAY COIL
>
\
PRO
PURPLE
GREEN
RED
BLUE
P B
PORTIONING 1
SAMPLER 1
2.00 SAMPLE
0.80 AIR
>
01 Mi—
CONTINU
I.60 BUFFER + INDICATOR
2.90 WASTE
PUMP
k
if
COLORIMETER RECORDER
15mm TUBULAR f/c
550 nm FILTERS
SAMPLING TIME: 2.0 MINUTES
WASH TUBES: ONE
FIGURE 1. ALKALINITY MANIFOLD
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STORE! No: Total 01002
ARSENIC Inorganic, Dissolved 00995
Inorganic, Total 00997
1. Scope and Application
1.1 The silver diethyldithiocarbamate method determines inorganic arsenic
when present in concentrations at or above 10 yg/1. The method is
applicable to most fresh and saline waters in the absence of high con-
centrations of chromium, cobalt, copper, mercury, molybdenum, nickel,
and silver.
1.2 Difficulties may be encountered with certain industrial waste materials
containing volatile substances. High sulfur content of wastes may
exceed removal capacity of the lead acetate scrubber.
2. Summary of Method
2.1 Arsenic in the sample is reduced to arsine, AsH,, in acid solution in
a hydrogen generator. The arsine is passed through a scrubber to remove
sulfide and is absorbed in a solution of silver diethyldithiocarbamate
dissolved in pyridine. The red complex thus formed is measured in a
spectrophotometer at 535 nm.
3. Comments
3.1 In analyzing most surface and ground waters, interferences are rarely
encountered. Industrial waste samples should be spiked with a known
amount of arsenic to establish adequate recovery.
3.2 It is essential that the system be air-tight during evolution of the
arsine, to avoid losses.
3.3 If concentration of sample and oxidation of any organic matter is
desired to measure organically-bound arsenic, refer to Standard Methods,
13th Ed., Method 104B, p 65, Procedure 4.a (1971).
13
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(Arsenic)
4. Precision and Accuracy
»
4.1 A synthetic unknown sample containing 40 ug/1, as As, with other
metals was analyzed in 46 laboratories. Relative standard deviation
was 13.8% and relative error was 0%.
5. Reference
5.1 The procedure to be used for this determination is found in:
Standard Methods for the Examination of Water and Wastewater,
13th Edition, p 62, Method 104A (1971).
14
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BIOCHEMICAL OXYGEN DEMAND
STORET No: 00310
1. Scope and Application
1.1 The biochemical oxygen demand test (BOD) is used for determining the
relative oxygen requirements of municipal and industrial wastewaters.
Application of the test to organic waste discharges allows calculation
of the effect of the discharges on the oxygen resources of the receiving
water. Data from BOD tests are used for the development of engineering
criteria for the design of wastewater treatment plants.
1.2 The BOD test is an empirical bioassay-type procedure which measures the
dissolved oxygen consumed by microbial life while assimilating and
oxidizing the organic matter present. The standard test conditions
include dark incubation at 20°C for a specified time period (often 5
days). The actual environmental conditions of temperature, biological
population, water movement, sunlight, and oxygen concentration cannot
be accurately reproduced in the laboratory. Results obtained must take
into account the above factors when relating BOD results to stream
oxygen demands.
2. Summary of Method
The sample of waste, or an appropriate dilution, is incubated for 5 days
at 20°C in the dark. The reduction in dissolved oxygen concentration
during the incubation period yields a measure of the biochemical oxygen
demand.
3. Comments
3.1 Because of the effect of local conditions, types of samples to be tested,
and the variabilities in bioassay procedures, no specific standard test
for BOD has been selected by the Water Quality Office.
15
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(BOD)
3.2 Determination of dissolved oxygen in the BOD test may be made by use
of either the Modified Winkler with Full-Bottle Technique (Pg. 53 )
or the Probe Method (Pg. 60 ) in this manual.
3.3 Additional information relating to oxygen demanding characteristics
of wastewaters can be gained by applying the Total Organic Carbon and
Chemical Oxygen Demand tests (see pp 221-229 and 17-28, respectively).
4. Precision and Accuracy
4.1 Seventy-seven analysts in fifty-three laboratories analyzed natural
water samples plus an exact increment of biodegradable organic compounds.
At a mean value of 194 mg/1 BOD, the standard deviation was ±40 mg/1.
4.2 There is no acceptable procedure for determining the accuracy of the
BOD test.
5. References
The procedure to be used for this determination is found in:
Standard Methods for the Examination of Water and Wastewater, 13th
Edition, P. 489, Method 219 (1971).
ASTM Standards, Part 23, Water; Atmospheric Analysis, P. 712,
Method D 2329-68 (1970).
16
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CHEMICAL OXYGEN DEMAND
STORE! No: 00540
1. Scope and Application
1.1 This method determines the quantity of oxygen required to oxidize
the organic matter in a waste sample, under specific conditions of
oxidizing agent, temperature, and time.
1.2 Since the test utilizes a rigorous chemical oxidation rather than a
biological process, the result has no defineable relationship to the
BOD of the waste. The test result should be considered as an inde-
pendent measurement of organic matter in the sample, rather than as
a substitute for the BOD test.
1.3 The method can be applied to domestic and industrial waste samples
having an organic carbon concentration greater than 15 mg/1. For
lower concentrations of carbon such as in surface water samples, the
Low Level Modification, Pg. 19, should be used. When the chloride
concentration of the sample exceeds 2000 mg/1>the modification for
saline waters, pg. 24, is required.
2. Summary of Method
2.1 Organic substances in the sample are oxidized by potassium dichromate
in 50% sulfuric acid solution at reflux temperature. Silver sulfate
is used as a catalyst and mercuric sulfate is added to remove chloride
interference. The excess dichromate is titrated with standard ferrous
ammonium sulfate, using orthophenanthroline ferrous complex as an
indicator.
17
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(COD)
3. Comments
3.1 To reduce loss of volatile organics, the flask should be cooled during
addition of the sulfuric acid solution.
4. Precision and Accuracy
4.1 Eighty-nine analysts in fifty-eight laboratories analyzed a distilled
water solution containing oxidizable organic material equivalent to
270 mg/1 COD. The standard deviation was ±27.5 mg/1 COD and the mean
recovery was 96% of the true value.
5. References
The procedure to be used for this determination is found in:
Standard Methods for the Examination of Water and Wastewater, 13th
Edition, P. 495 Method 220 (1971).
ASTM Standards, Part 23, Water; Atmospheric Analysis, P. 246
Method D 1252-67 (1970).
18
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CHEMICAL OXYGEN DEMAND
(Low Level)
STORE! NO. 00555
1. Scope and Application
1.1 The scope of this modification of the Chemical Oxygen Demand (COD)
test is the same as for the high level test. It is applicable to
the analysis of surface waters, domestic and industrial wastes with
low demand characteristics.
1.2 This method (low level) is applicable for samples having a COD in the
range of 5-50 mg/1 COD.
I :
2. Summary of Method i
i •
i i
2.1 Organic and oxidizable inorganic substances in an aqueous sample are
oxidized by potassium dichromate solution in 50 percent (by volume)
sulfuric acid solution. The excess dichromate is titrated with standard
ferrous ammonium sulfate using orthophenanthroline ferrous complex
(ferroin) as an indicator.
5. Sampling and Preservation
5.1 Collect the samples in glass bottles, if possible. Use of plastic
containers is permissible if it is known that no organic contaminants
are present in the containers.
5.2 Biologically active samples should be tested as soon as possible.
Samples containing settleable material should be well mixed, pre-
ferably homogenized, to permit removal of representative aliquots.
5.5 Samples may be preserved with sulfuric acid at a rate of 2 ml of
cone. H2SO. per liter of sample.
4. Interferences
4.1 Traces of organic material either from the glassware or atmosphere may
cause a gross, positive error.
19
-------
(Chemical Oxygen Demand)
(Low Level)
4.1.1 Extreme care should be exercised to avoid inclusion of
organic materials in the distilled water used for reagent
preparation or sample dilution.
4.1.2 Glassware used in the test should be conditioned by running
blank procedures to eliminate traces of organic material.
4.2 Volatile materials may be lost when the sample temperature rises during
the sulfuric acid addition step.
4.3 Chlorides are quantitatively oxidized by dichromate and represent a
positive interference. Mercuric sulfate is added to the digestion flask
to complex the chlorides, thereby effectively eliminating the inter-
ference on all but brine and estuarine samples.
5. Apparatus
5.1 Reflux apparatus - Glassware should consist of a 500 ml Erlenmeyer
flask or a 300 ml round bottom flask made of heat-resistant glass
connected to a 12 inch Allihn condenser by means of a ground glass
joint. Any equivalent reflux apparatus may be substituted provided that
a ground-glass connection is used between the flask and the condenser.
6. Reagents
6.1 Distilled water. Special precautions should be taken to insure that
distilled water used in this test be low in organic matter.
6.2 Standard potassium dichromate solution (0.025 N) - Dissolve 12.259 g
K Cr?0_, primary standard grade, previously dried at 103°C for two
hours, in distilled water and dilute to 1.0 1. Mix this solution
thoroughly then dilute 100 ml to 1.0 1 with distilled water.
6.3 Sulfuric acid reagent - Cone. H_S04 containing 23.5 g silver sulfate,
Ag-SO., per 9 Ib. bottle (one to two days required for dissolution).
20
-------
(Chemical Oxygen Demand)
(Low Level)
6.4 Standard ferrous ammonium sulfate (0.025 N) - Dissolve 98 g o£
Fe(NH4)2(S04)2.6H20 in distilled water. Add 20 ml of cone. H_SO ,
cool and dilute to 1.0 1. Dilute 100 ml of this solution to 1.0 1
with distilled water. This solution must be standardized daily
against K_Cr20_ solution.
6.4.1 Standardization - To 15 ml of distilled water add 10 ml of
0.025 N Kr2Cr207 solution. Add 20 ml of H2S04 and cool.
Titrate with ferrous ammonium sulfate using 1 drop of ferroin
indicator. The color change is sharp, going from blue-green
to reddish-brown.
(ml K2Cr20?)(0.025)
Normality = ml Fe(NH4)2(S04)2
6.5 Mercuric sulfate - Powdered HgSO..
6.6 Phenanthroline ferrous sulfate (ferroin) indicator solution - Dissolve
1.48 g of l-10-(ortho)-phenanthroline monohydrate, together with
0.70 g of FeS04-7H 0 in 100 ml of water. This indicator may be pur-
chased already prepared.
6.7 Silver sulfate - Powdered Ag2S04<
6.8 Sulfuric acid (sp. gr. 1.84) - Concentrated H2SO .
7. Procedure
7.1 Place several boiling stones in the reflux flask, followed by 1 g of
HgS04. Add 5.0 ml cone. JUSCK (6.8); swirl until mercuric sulfate
has dissolved. Place reflux flask in an ice bath and slowly add, with
swirling, 25.0 ml of 0.025 N K^^Cy Now add 70.0 ml of sulfuric
acid-silver sulfate solution (6.3) to the cooled reflux flask, again
using slow addition with swirling motion.
21
-------
(Chemical Oxygen Demand)
CLow Level)
7.2 With the reflux flask still in the ice bath, place 50.0 ml of sample
or a sample aliquot diluted to 50.0 ml into the reflux flask.
Caution: Care must be taken to assure that the contents of the flask
are well mixed. If not, superheating may result, and the mixture may
be blown out of the open end of the condenser. Attach the flask to
the condenser and start the cooling water.
7.3 Apply heat to the flask and reflux for 2 hours. For some waste waters,
the 2-hour reflux period is not necessary. The time required to give
the maximum oxidation for a waste water of constant or known com-
position may be determined and a shorter period of refluxing may be
permissible.
7.4 Allow the flask to cool and wash down the condenser with about 25 ml
of water. If a round bottom flask has been used, transfer the mixture
to a 500-ml Erlenmeyer flask, washing out the reflux flask 3 or 4
times with water. Dilute the acid solution to about 300 ml with water
and allow the solution to cool to about room temperature. Add 8 to 10
drops of ferroin indicator to the solution and titrate the excess
dichromate with 0.025 N ferrous ammonium sulfate solution to the
end point. The color change will be sharp, changing from a blue-
green to a reddish hue.
7.5 Blank - Simultaneously run a blank determination following the details
given in 7.1 and 7.2, but using low COD water in place of the sample.
8. Calculation
8.1 Calculate the COD in the sample in mg/1 as follows:
rrm /T+ (A - B) N X 8000
COD, mg/liter = '—•=
where:
22
-------
CChemical Oxygen Demand)
(low Level)
A = mi Hi liters of Fe (NH.) _ (SO.) _ solution required for
titration of the blank,
B = milliliters of Fe (NH.) „ (SO.) 2 solution required for
titration of the sample,
N = normality of the Fe(NH.)2(SO ) solution, and
S = milliliters of sample used for the test.
9. Precision ji
9.1 The precision of the low level test described in the foregoing
material has not been determined by collaborative testing.
23
-------
CHEMICAL OXYGEN DEMAND
(High Level for Saline Waters)
STORE! NO. 00540
1. Scope and Application
1.1 When the chloride level exceeds 1000 mg/1 the minimum accepted value
for the COD will be 250 mg/1. COD levels which fall below this value
are highly questionable because of the high chloride correction which
must be made.
2. Summary of Method
2.1 Organic and oxidizable inorganic substances in an aqueous sample are
oxidized by potassium dichromate solution in 50 percent (by volume)
sulfuric acid solution. The excess dichromate is titrated with
standard ferrous ammonium sulfate using orthophenanthroline ferrous
complex (ferroin) as an indicator.
3. Sample Handling and Preservation
3.1 Collect the samples in glass bottles, if possible. Use of plastic
containers is permissible if it is known that no organic contaminants
are present in the containers.
3.2 Biologically active samples should be tested as soon as possible.
Samples containing settleable material should be well mixed, pre-
ferably homogenized, to permit removal of representative aliquots.
3.3 Samples are preserved by the addition of 2 ml of cone. H2S04 per liter
of sample.
4. Interferences
4.1 Traces of organic material either from the glassware or atmosphere
may cause a gross, positive error.
4.1.1 Extreme care should be exercised to avoid inclusion of organic
materials in the distilled water used for reagent preparation
24
-------
(COD - High Level for
Saline Waters)
or sample dilution.
4.1.2 Glassware used in the test should be conditioned by running
blank procedures to eliminate traces of organic material.
4.2 Volatile materials may be lost when the sample temperature rises
during the sulfuric acid addition step.
4.3 Chlorides are quantitatively oxidized by dichromate and represent
a positive interference. Mercuric sulfate is added to the digestion
i
flask to complex the chlorides, thereby effectively eliminating the
interference on all but brine samples.
5. Apparatus
5.1 Reflux apparatus - Glassware should consist of a 500 ml Erlenmeyer
flask or a 300 ml round bottom flask made of heat-resistant glass
connected to a 12 inch Allihn condenser by means of a ground glass
joint. Any equivalent reflux apparatus may be substituted provided
that a ground-glass connection is used between the flask and the con-
denser.
6. Reagents
6.1 Standard potassium dichromate solution, (0.25 N) : Dissolve 12.2588 g
of K-Cr-0 , primary standard grade, previously dried for 2 hours at
103°C in water and dilute to 1.0 liter.
6.2 Sulfuric acid reagent: Cone. H2S04 containing 23.5 g silver sulfate,
Ag?SO., per 9 Ib. bottle (1 to 2 days required for dissolution).
6.3 Standard ferrous ammonium sulfate, 0.250 N: Dissolve 98 g of
Fe(NH4)2(S04)2.6H20 in distilled water. Add 20 ml of cone. H2S04,
cool and dilute to 1.0.1. This solution must be standardized
against the standard potassium dichromate solution daily.
25
-------
(COD - High Level for
Saline Wa
6.3.1 Standardization: Dilute 25.0 ml of standard dichromate
solution to about 250 ml with distilled water. Add 75 ml cone.
sulfuric acid. Cool, then titrate with ferrous ammonium sulfate
titrant, using 10 drops of ferroin indicator.
(ml K Cr20 ) (0.25)
ml Fe(NH4)2(S04)2
6.4 Mercuric sulfate - Powdered HgSO..
6.5 Phenanthroline ferrous sulfate (ferroin) indicator solution - Dissolve
1.48 g of l-10-(ortho)-phenanthroline monohydrate, together with 0.70 g
of FeS0..7H20 in 100 ml of water. This indicator may be purchased
already prepared.
6.6 Silver sulfate - Powdered Ag-SO..
6.7 Sulfuric acid (sp. gr. 1.84) - Concentrated H-SO..
7. Procedure
7.1 Pipet a 50 ml aliquot of sample not to exceed 800 mg/1 of COD into a
500 ml, flat bottom, Erlenmeyer flask. Add 25 ml of 0.25 N Kr2Cr207,
then 5.0 ml of cone. H^SO. (containing no silver sulfate). Add HgSO.
in the ratio of 10 mg to 1 mg chloride, based upon the mg of chloride
in the sample aliquot. Swirl until all the mercuric sulfate has dissolved.
Carefully add 70 ml of sulfuric acid-silver sulfate solution and gently
swirl until the solution is thoroughly mixed. Glass beads should be added
to the reflux mixture to prevent bumping, which can be severe and
dangerous. (CAUTION: The reflux mixture must be thoroughly mixed before
heat is applied. If this is not done, local heating occurs in the bottom
of the flask, and the mixture may be blown out of the condenser).
26
-------
(COD - High Level for
Saline Waters)
7.1.1 If volatile organics are present in the sample, use an Allihn
condenser and add the sulfuric acid-silver sulfate solution
through the condenser, while cooling the flask, to reduce
loss by volatilization.
7.2 Attach the flask to the condenser and reflux the mixture for two hours,
7.3 Cool, and wash down the interior of the condenser with 25 ml of
distilled water. Disconnect the condenser and wash the flask and
condenser joint with 25 ml of distilled water. Remove the condenser
and carefully add to the flask 175 ml of distilled water so that the
total volume is 350 ml. Cool to room temperature.
7.4 Titrate with standard ferrous ammonium sulfate using 10 drops of
ferroin indicator. (This amount must not vary from blank, sample and
standardization). The color change is sharp, going from blue-green
to reddish-brown and should be taken as the end point although the
blue-green color may reappear within minutes.
7.5 Run a blank, using 50 ml of distilled water in place of the sample
together with all reagents and subsequent treatment.
7.6 For COD values greater than 800 mg/1, a sjnaller aliquot of sample
should be taken; however, the volume should be readjusted to 50 ml
with distilled water having a chloride concentration equal to the
sample.
7.7 Chloride correction* - Prepare a standard curve of COD versus mg/1
*Bums, E. R., Marshall, C., Journal WPCF, Vol. 37, pp 1716-1721 (1965)
27
-------
(COD - High. Level for
Saline Waters)
of chloride, using sodium chloride solutions of varying concen-
trations following exactly the procedure outlined. The chloride
interval, as a minimum should be 4000 mg/1 up to 20,000 mg/1
chloride. Lesser intervals of greater concentrations must be run
as per the requirements of the data, but in no case must extra-
polation be used.
8. Calculation
8.1 mg/1 COD =CCA - B) C X 8000-500] ^2Q
& ml sample
where:
COD = chemical oxygen demand from dichromate
A = ml Fe(NH4)2(S04)2 for blank;
B = ml Fe(NH4)2(S04)2 for sample;
C = normality of Fe(NH4)2(S04)2;
D = chloride correction from curve (step 7.7).
1..20 = compensation factor to account for the extent of chloride
oxidation which is dissimilar in systems containing organic
and nonorganic material.
9. Precision and Accuracy
9.1 Precision and accuracy data are not available at this time.
28
-------
CHLORIDE
STORET Number: 00940
1. Scope and Application
1.1 This method is applicable to drinking waters and surface waters,
domestic and industrial wastes, and saline waters.
1.2 The method is suitable for all concentration ranges of chloride
content; however, in order to avoid large titration volumes, use
a sample aliquot containing not more than 10 to 20 mg Cl per 50 ml.
1.3 Automated titration may be used.
2. Summary of Method
2.1 Dilute mercuric nitrate solution is added to an acidified sample
in the presence of mixed diphenylcarbazone - bromophenol blue
indicator. The end point of the titration is the formation of
the blue - violet mercury diphenylcarbazone complex.
3. Comments
3.1 Anions and cations at concentrations normally found in surface
waters do not interfere.
3.2 Sulfites interfere. If presence is suspected, oxidize by treating
50 ml of sample with 0.5 to 1 ml of H,,CL.
4. Precision and Accuracy
4.1 Forty-two analysts in eighteen laboratories analyzed synthetic
water samples containing exact increments of chloride, with the
following results:
29
-------
(Chloride)
Increment as
Chloride
rag/liter
17
18
91
97
382
398
Precision as
Standard Deviation
mg/liter
1.54
1.32
2.92
3.16
11.7
11.8
Accuracy as
Bias, Bias,
% mg/liter
+2.16 +0.4
+3.50 +0.6
+0.11 +0.1
-0.51 -0.5
-0.61 -2.3
-1.19 -4.7
(FWPCA Method Study 1, Mineral and Physical Analyses)
4.2 In a single laboratory (AQC), using surface water samples at an
average concentration of 34 mg Cl/1, the standard deviation was
±1.0.
5. Reference
5.1 The procedure to be used for this determination is found in:
Standard Methods for the Examination of Water and Wastewater,
13th Edition, p. 97, Method 112B (1971).
ASTM Standards, Part 23, Water; Atmospheric Analysis, p. 24,
Method 512-67 (1970).
30
-------
CHLORIDE
(Automated Ferricyanide Method)
STORE! NO. 00940
1. Scope and Application
1.1 This automated method is applicable on surface water, domestic and
industrial wastes, and saline waters. The applicable range is 1 to
250 mg Cl/1. Approximately 15 samples per hour can be analyzed.
2. Summary of Method
2.1 Thiocyanate ion (SCN) is liberated from mercuric thiocyanate, through
sequestration of mercury by chloride ion to form un-ionized mercuric
chloride. In the presence of ferric ion, the liberated SCN forms
highly colored ferric thiocyanate, in concentration proportional to
the original chloride concentration.
3. Sample Handling and Preservation
3.1 No special requirements.
4. Interferences
4.1 No significant interferences.
5. Apparatus
5.1 Technicon AutoAnalyzer consisting of:
5.1.1 Sampler I.
5.1.2 Continuous filter.
5.1.3 Manifold.
5.1.4 Proportioning pump.
5.1.5 Colorimeter equipped with 15 mm tubular flow cell and
480 nm filters.
5.1.6 Recorder.
6. Reagents
6.1 Ferric Ammonium Sulfate: Dissolve 60 g of FeNH CSO.) .12 HO in
approximately 500 ml distilled water. Add 355 ml of cone. HNO and
31
-------
(Chloride)
dilute to 1 liter with distilled water. Filter.
6.2 Saturated Mercuric Thiocyanate: Dissolve 5 g of Hg(SCN)- in 1 liter
of distilled water. Decant and filter a portion of the saturated
supernatant liquid to use as the reagent and refill the bottle with
distilled water.
6.3 Stock Solution (0.0141 N NaCl): Dissolve 0.8241 g of pre-dried (140°C) NaCl
in distilled water. Dilute to 1 liter- 1 ml = 0.5 mg Cl~.
6.3.1 Prepare a series of standards by diluting suitable volumes of
stock solution to 100.0 ml with distilled water. The following
dilutions are suggested:
ml of Stock Solution Cone., mg/1
0.2 1.0
1.0 5.0
2.0 10
4.0 20
8.0 40
15.0 75
20.0 100
30.0 150
40.0 200
50.0 250
7. Procedure
7.1 No advance sample preparation is required. Set up manifold as shown
in Figure 1. For water samples known to be consistently low in
chloride content, it is advisable to use only one distilled water in-
take line.
7.2 Allow both colorimeter and recorder to warm up for 30 minutes. Run a
baseline with all reagents, feeding distilled water through the sample
line. Adjust dark current and operative opening on colorimeter to
obtain stable baseline.
32
-------
(Chloride)
7.3 Place distilled water wash tubes in alternate openings in sampler
and set sample timing at 2.0 minutes.
7.4 Place working standards in sampler in order of decreasing concentrations.
Complete filling of sampler tray with unknown samples.
7.5 Switch sample line from distilled water to sampler and begin analysis.
8. Calculation
8.1 Prepare standard curve by plotting peak heights of processed standards
against known concentrations. Compute concentration of samples by
i
comparing sample peak!heights with standard curve.
i
9. Precision and Accuracy
9.1 In a single laboratory, (AQC), using surface water samples at con-
centrations of 1, 100, and 250 mg Cl /I, the standard deviation was ±0.3.
9.2 In a single laboratory (AQC), using surface water samples at concen-
trations of 10 and 100 mg Cl/1, recoveries were 97% and 104%,
respectively.
Reference
1. J. E. O'Brien, "Automatic Analysis of Chlorides in Sewage," Waste Engr.,
33, 670-672 (Dec. 1962).
33
-------
SMALL
MIXING
COILS
WASTE
COLORIMETER
15mm TUBULAR f/c
480 nm FILTERS
IX
ml/min
2.00
BLUE
BLUE
W
W
PROPORTIONING
PUMP
1.20 SAMPLE
1.20
DISTILLED
WATER
AIR
CONTINUOUS FILTER
1.60 Fe NH4(S04J2
0.60
Hg (SCN)
2.50
WASTE
RECORDER
SAMPLING TIME: 2.0 MINUTES
WASH TUBES: ONE
FIGURE 1. CHLORIDE MANIFOLD
-------
CHLORINE REQUIREMENT
STORE! NO.
1. Scope and Application
1.1 This method is applicable to drinking water, surface waters,
domestic and industrial wastes and saline waters. Limitations of
the method are implied in paragraph 1.2, below.
1.2 Chlorine requirement is defined as the amount of chlorine which
must be added per unit volume of sample to produce a desired result
under stated conditions. It is therefore applicable to control of
i
j
coliform densities, destruction of certain chemical compounds and
odorous materials, and establishment of specified chlorine residuals.
1.3 Chlorine requirement is not an absolute value and cannot be used
to compare results from time to time or place to place.
2. Summary of Method
2.1 A solution of known chlorine content is added incrementally to a
series of sample aliquots. At the end of the stipulated contact
time or when the desired result has been achieved the residual
chlorine is measured by the appropriate method.
3. Comments
3.1 In cases where the desired result is a specified residual chlorine
concentration, it is important that the same method for chlorine
measurement be used for both laboratory testing and operational
control.
3.2 In reporting results all of the pertinent information must be in-
cluded: the conditions of chlorination, such as pH, temperature and
contact time; the method used for determining the result and the
chlorine required to produce the desired result (i.e., the chlorine
requirement).
36
-------
(Chlorine)
4. Precision and Accuracy
4.1 The nature of this test precludes the use of accuracy and
precision statement.
5. Reference
The procedure to be used for this determination is found in:
Standard Methods for the Examination of Water and
Wastewaters, 13th Edition, pp 388-391, Method No.
205A and 205B (1971).
37
-------
COLOR
STORE! NO. 00080
1. Scope and Application
1.1 The Platinum-Cobalt method is useful for measuring color of water
derived from naturally occurring materials, I.e., vegetable residues
such as leaves, barks, roots, humus and peat materials. The method
is not applicable to color measurement on waters containing highly
colored industrial wastes.
Note - The Spectrophotometric and Tristimulus methods are useful
for detecting specific color problems. The use of these methods,
however, is laborious and unless determination of the hue, purity,
and luminance is desired, they are of limited value.
2. Summary of Method
2.1 Color is measured by visual comparison of the sample with platinum-
cobalt standards. One unit of color is that produced by 1 mg/1
platinum in the form of the chloroplatinate ion.
3. Interferences
3.1 Since very slight amounts of turbidity interfere with the determination,
samples showing visible turbidity should be clarified by centrifugation.
4. Sample Handling and Preservation
4.1 Representative samples shall be taken in scrupulously clean glassware.
4.2 Since biological activity may change the color characteristics of a
sample, the determination should be made as soon as possible. Refri-
geration at 4°C is recommended.
5. Apparatus
5.1 Nessler tubes - Matched, tall form, 50 ml capacity.
38
-------
(Color)
6. Reagents
6.1 Standard chloroplatinate solution. Dissolve 1.246 g potassium chloro-
platinate, K2PtCl,, (equivalent to 0.500 g metallic Pt) and 1 g
crystalline cobaltous chloride, CoCl2.6H20, in distilled water con-
taining 100 ml of cone. HC1. Dilute to 1 liter with distilled water.
This standard solution is equivalent to 500 color units.
7. Preparation of Standards
7.1 Prepare standards in increments from 5 to 70 units.
The following series is suggested:
ml of Standard Solution
Diluted to 50.0 ml Color in
with Distilled Water Chloroplatinate Units
0.0 0
0.5 5
1.0 10
1.5 15
2.0 20
2.5 25
3.0 30
3.5 35
4.0 40
4.5 45
5.0 50
6.0 60
7.0 70
7.2 Protect these standards against evaporation and contamination by use
of clean, inert stoppers.
Note - The standards also must be protected aganst the absorption
of ammonia since an increase in color will result.
8. Procedure
8.1 Apparent color - Observe the color of the sample by filling a matched
Nessler tube to the 50 ml mark with the water and compare with standards.
This comparison is made by looking vertically downward through the
39
-------
CColor)
tubes toward a white or specular surface placed at such an angle
that light is reflected upward through the columns of liquid. If
turbidity has not been removed by the procedure given in 8.2, report
the color as "apparent color." If the color exceeds 70 units,
dilute the sample with distilled water in known proportions until
the color is within the range of the standards.
8.2 True color - Remove turbidity by centrifuging the sample until the
supernatant is clear.. The time required will depend upon the nature
of the sample, the speed of the motor, and the radius of the centri-
fuge, but rarely will more than one hour be necessary. Compare the
centrifuged sample with distilled water to insure that turbidity has
been removed. If the sample is clear, then compare with standards as
given in 8.1.
9. Calculation
9.1 Calculate the color units by means of the following equation:
„ , .... A x 50
Color units =
V
Where: A = estimated color of diluted sample.
V = ml sample taken for dilution.
9.2 Report the results in whole numbers as follows:
Color Units Record to Nearest
1-50 1
51-100 5
101-250 10
251-500 20
10. Precision and Accuracy
10.1 Precision and accuracy data are not available at this time.
Reference - Standard Methods for the Examination of Water and Waste-
water, 13th. Edition, p. 160, Method 118 (1971) •
40
-------
CYANIDE
1. Scope and Application
1.1 This method is applicable to the determination of cyanide in surface
waters, domestic and industrial wastes, and saline waters.
1.2 The titration procedure using silver nitrate with p-dimethylamino-
benzalrhodanine indicator is used for measuring concentrations of
cyanide exceeding 1 mg/1 (0.2 mg/200 ml of absorbing liquid).
1.3 The colorimetric procedure is used for concentrations below 1 mg/1 of
cyanide and is sensitive to about 5 yg/1.
2. Summary of Method
2.1 The cyanide as hydrocyanic acid (HCN) is released from metallic cyanide
complex ions by means of a reflux-distillation operation and absorbed
in a scrubber containing sodium hydroxide solution. The cyanide ion
in the absorbing solution is then determined by volumetric titration
or colorimetrically.
2.2 The colorimetric measurement employs the pyridine-pyrazolone reaction
in which the cyanide is coupled with free chlorine to form cyanogen
chloride and then with pyridine to a glutaconic aldehyde. The aldehyde
then reacts with l-phenyl-3-methyl-5-pyrazolone to form a highly colored
blue dye.
2.3 The titrimetric measurement uses a standard solution of silver nitrate
to titrate cyanide in the presence of a silver sensitive indicator.
3. Definitions
3.1 Cyanide is defined as cyanide ion and complex cyanides converted to
hydrocyanic acid (HCN) by reaction in a reflux system of a mineral acid
in the presence of magnesium and mercuric ions.
41
-------
(Cyanide)
4. Sampling Handling and Preservation
4.1 The sample should be collected in plastic bottles of 1 liter or larger
size. All bottles must be thoroughly cleansed and thoroughly rinsed
to remove soluble material from containers.
4.2 Samples must be preserved with 2 ml of 10 N sodium hydroxide per liter
of sample (pH of 11) at the time of collection.
4.3 Samples should be analyzed as rapidly as possible after collection.
If storage is required, the samples should be stored in a refrigerator
or in an ice chest filled with water and ice to maintain temperature at
4O/-i
C.
5. Interferences
5.1 Interferences are eliminated or reduced by using the distillate obtained
with the preliminary screening procedure.
5.2 Sulfides are an interference that should be removed prior to distillation.
Remove sulfides with pH adjustment to >11, addition of lead carbonate and
mixing. Filter sample to remove lead sulfide. Repeat until no more lead
sulfide is formed as evidenced by whiteness of the lead carbonate.
5.3 Oxidizing substances interfere and should be treated with ascorbic acid.
6. Apparatus
6.1 Reflux distillation apparatus such as shown in Figure 1 or Figure 2.
The boiling flask should be of 1 liter size with inlet tube and pro-
vision for condenser. The gas absorber may be a Fisher-Milligan scrubber.
6.2 Microburet, 5.0 ml (for titration).
6.3 Spectrophotometer suitable for measurements at 620 nm with a 1.0 cm cell
or larger.
42
-------
ALLIHN CONDENSER —
AIR INLET TUBE
— CONNECTING TUBING
ONE LITER
BOILING FLASK
SUCTION
GAS ABSORBER
FIGURE 1
CYANIDE DISTILLATION APPARATUS
-------
COOLING WATER
INLET
SCREW CLAMP
I
HEATER -*
TO LOW VACUUM
SOURCE
-*• ABSORBER
DISTILLING FLASK
O
FIGURE 2
CYANIDE DISTILLATION APPARATUS
45
-------
(Cyanide)
7. Reagents
7.1 Sodium hydroxide solution, 1 N. Dissolve 40 g of NaOH in distilled
water, and dilute to a liter with distilled water.
7.2 Lead carbonate.
7.3 Ascorbic acid.
7.4 Mercuric chloride solution. Dissolve 34 g HgC^ in 500 ml distilled
water.
7.5 Magnesium chloride solution. Dissolve 51 g MgCl~.6H20 in 100 ml
distilled water. '
7.6 Sulfuric acid, concentrated.
7.7 Sodium dihydrogenphosphate, 1 M. Dissolve 138 g of Na^PC^.l^O in one
liter of distilled water. Refrigerate this solution.
7.8 Stock cyanide solution. Dissolve 2.51 g of KCN and 2 g KOH in one liter
of distilled water. Standardize with 0.0192 N AgNOj. Dilute to
appropriate concentration so that 1 ml = 1 mg CN~.
7.9 Standard cyanide solution, intermediate. Dilute 10 ml of stock
(1 ml = 1 mg CN) to a liter of distilled water (1 ml = 10 yg).
7.10 Standard cyanide solution. Prepare fresh daily by diluting 100 ml of
intermediate cyanide solution to a liter of distilled water and store in
a glass stoppered bottle. One ml = 1.0 yg CN (1.0 mg/1).
7.11 Standard silver nitrate solution, 0.0192 N. Prepare by crushing
approximately 5 g AgNOg crystals and drying to constant weight at 40°C.
Weigh out 3.2647 g of dried AgNO,, dissolve in water, and dilute to 1.0
liter (1 ml = 1 mg CN).
47
-------
(Cyanide)
7.12 Rhodanine indicator. Dissolve 20 mg of p-dimethylamino-benzal-
rhodanine in 100 ml of acetone.
7.13 Chloramine T solution. Dissolve 1.0 g of white water soluble Chloramine
T in 100 ml of distilled water and refrigerate until ready to use.
Prepare fresh weekly.
7.14 Pyridine-pyrazolone solution.
7.14.1 One-phenyl-S-methyl-S-pyrazolone reagent. Weigh 0.25 g of
3-methyl-l-phenyl-2-pyrazolone-5-one and dissolve in 50 ml of
distilled water by heating to 60°C. Cool after reagent is
in solution.
7.14.2 Three, 3'Dimethyl-l,l'-diphenyl-4,4f-bi-2 pyrazolone - 5,5'
dione (bispyrazolone). Dissolve 0.01 g of bispyrazolone in
10 ml of pyridine.
7.14.3 Pour solution 7.14.1 through nonacid-washed filter paper.
Collect the filtrate. Through the same filter paper pour
solution 7.14.2 collecting the filtrate in the same container
as filtrate from 7.14.1. Mix until the filtrates are homo-
geneous. The mixed reagent develops a pink color but this
does not affect the color production with cyanide if used with-
in 24 hours of preparation.
8. Procedure
8.1 Place 500 ml of sample, or an aliquot diluted to 500 ml in the 1-liter
boiling flask. Add 50 ml of 1 N sodium hydroxide (7.1) to the absorbing
tube and dilute if necessary with distilled water to obtain an adequate
depth of liquid in the absorber. Connect the boiling flask, condenser,
absorber and trap in the train.
48
-------
(Cyanide)
8.2 Start a slow stream of air entering the boiling flask by adjusting
the vacuum source. Adjust the vacuum so that approximately 1 bubble
of air per second enters the boiling flask through the air inlet tube.
(Caution: The bubble rate will not remain constant after the reagents
have been added and while heat is being applied to the flask. It will
be necessary to readjust the air rate occasionally to prevent the
solution in the boiling flask from backing up into the air inlet tube).
8.3 Add 10 ml of mercuric chloride solution (7.4) and 40 ml of magnesium
chloride solutions (7.5) through the air inlet tube. Rinse the air inlet
tube with a few ml of distilled water and allow the air flow to mix the
contents of the flask for at least 3 minutes.
8.4 Slowly add 25 ml of concentrated sulfuric acid (7.6) through the air
inlet tube and rinse with distilled water.
8.5 Heat the solution to boiling, taking care to prevent the solution from
backing up into and overflowing from the air inlet tube. Reflux for
one hour. Turn off heat and continue the airflow for at least 15 minutes
After cooling of the boiling flask disconnect absorber and close off the
vacuum source.
8.6 Drain the solution from the absorber into a 250 ml volumetric flask
and bring up to volume with distilled water washings from the absorber
tube.
8.7 Withdraw 50 ml of the solution from the volumetric flask and transfer
to a 100-ml volumetric flask. Add 10 ml of sodium phosphate solution
(7.7) and 0.2 ml of Chloramine T solution (7.13) and mix. Add an
additional 5 ml of the sodium phosphate (7.7), followed by 5 ml of
49
-------
(Cyanide)
mixed pyridine-pyrazolone solution, (7.14.3), bring to mark with
distilled water and mix. Allow 40 minutes for color development.
8.8 Read absorbance at 620 nm using at least a 1.0 cm cell.
8.9 Prepare a series of standards by diluting suitable volumes of standard
solution to 500.0 ml with distilled water as follows:
ml of Standard Solution Cone., When Diluted to
(1.0 ml = 1 yg CN) 500 ml, mg/1 CN
0 (Blank) 0
5.0 0.01
10.0 0.02
20.0 0.04
50.0 0.10
100.0 0.20
150.0 0.30
200.0 0.40
8.9.1 Standards must be treated in the same manner as the samples,
as outlined in 8.1 through 8.8 above.
8.9.2 Prepare a standard curve by plotting absorbance of standards
vs. cyanide concentrations.
8.9.3 Subsequently, at least two standards (a high and a low) should
be treated as in 8.9.1 to verify standard curve. If results
are not comparable (±20%), a complete new standard curve must
be prepared.
8.9.4 To check the efficiency of the sample distillation, add an
increment of cyanide from either the intermediate standard
(7.9) or the working standard (7.10) to insure a level of 10
pg/1 or a significant increase in absorbance value. Proceed
with the analysis as in Procedure (8.) using the same flask
and system from which the previous sample was just distilled.
50
-------
(Cyanide)
8.10 Alternatively, if the sample contains more than 1 mg of CN transfer
the distillate, or a suitable aliquot diluted to 250 ml, to a 500-ml
Erlenmeyer flask. Add 10-12 drops of the benzalrhodanine indicator.
8.11 Titrate with standard silver nitrate to the first change in color
from yellow to brownish-pink. Titrate a distilled water blank using
the amount of sodium hydroxide and indicator as the sample.
8.12 The analyst should familiarize himself with the end point of the
titration and the amount of indicator to be used before actually
titrating the samples. A 5 or 10 ml microburet may be conveniently
|
used to obtain a more precise titration.
9. Calculation
9.1 Using the colorimetric procedure, calculate concentration of CN, mg/1,
directly from prepared standard curve.
9.2 Using the titrimetric procedure, calculate concentration of CN as
follows:
w fl ^ (A-B) x 1000 250
' ° Vol. of original sample Vol. of aliquot titrated
where:
A = volume of AgNO, for titration of sample.
B = volume of AgNO_ for titration of blank.
0. Precision and Accuracy
10.1 A synthetic sample prepared by the Analytical Reference Service (PHS)
at a known concentration of 0.02 mg/1 CN was analyzed by 47 analysts;
the data showed a standard deviation of 0.035 mg/1 for the titrimetric
procedure and 0.020 mg/1 for the colorimetric procedure. Similarly, at
a concentration of 1.10 mg/1 of CN, the data showed a standard deviation
51
-------
(Cyanide)
of 0.333 mg/1 for the titrimetric procedure and 0.306 mg/1 for the
colorimetric procedure.
References
1. Bark, L. S., and Higson, H. G. Investigation of reagents for the colorimetric
determination of small amounts of cyanide. Talanta, 2:471-479 (1964).
2. Elly, C. T. Recovery of cyanides by modified Serfass distillution. Journal
Water Pollution Control Federation, 40:848-856 (1968).
52
-------
DISSOLVED OXYGEN
(Modified Winkler With Full-Bottle Technique)
1. Scope and Application ' STORE! NO. 00500
1.1 This method is applicable for use with most wastewaters and streams
that contain nitrate nitrogen and not more than 1 mg/1 of ferrous
iron. Other reducing or oxidizing materials should be absent. If
1 ml fluoride solution is added before acidifying the sample and
there is no delay in titration, the method is also applicable in the
presence of 100-200 mg/1 ferric iron.
1.2 The Dissolved Oxygen Probe technique (see p 60) gives comparable
results on all sample types.
1.3 The azide modification is not applicable under the following condi-
tions: (a) samples containing sulfite, thiosulfate, polythionate,
appreciable quantities of free chlorine or hypochlorite; (b) samples
high in suspended solids; (c) samples containing organic substances
which are readily oxidized in a highly alkaline solution, or which are
oxidized by free iodine in an acid solution; (d) domestic sewage; (e)
biological floes; and (f) where sample color interferes with endpoint
detection. In instances where the azide modification is not appli-
cable, the DO probe should be used.
2. Summary of Method
2.1 The sample is treated with manganous sulfate, potassium hydroxide, and
potassium iodide (the latter two reagents combined in one solution)
and finally sulfuric acid. The initial precipitate of manganous hydrox-
ide, Mn(OH)_, combines with the dissolved oxygen in the sample to form
a brown precipitate, manganic hydroxide, Mn 0(OH)_. Upon acidification,
the manganic hydroxide forms manganic sulfate which acts as an oxidizing
agent to release free iodine from the potassium iodine. The iodine,
which is stoichiometrically equivalent to the dissolved oxygen in the
sample is then titrated with sodium thiosulfate.
53
-------
(Dissolved Oxygen)
3. Interferences
3.1 There are a number of interferences to the dissolved oxygen test,
including oxidizing and reducing agents, nitrate ion, ferrous iron,
and organic'matter.
3.2 Various modifications of the original Winkler procedure for dissolved
oxygen have been developed to compensate or eliminate interferences.
The Alsterberg modification is commonly used to successfully eliminate
the nitrite interference, the Rideal-Stewart modification is designed
to eliminate ferrous iron interference, and the Theriault procedure is
used to compensate for high concentration of organic materials.
3.3 Most of the common interferences in the Winkler procedure may be over-
come by use of the dissolved oxygen probe.
4. Sample Handling and Preservation
4.1 Where possible, collect the sample in a 300 ml BOD incubation bottle.
Special precautions are required to avoid entrainment or solution of
atmospheric oxygen or dissolution of dissolved oxygen.
4.2 Where samples are collected from shallow depths (less than 5 feet),
use of an APHA-type sampler is recommended. Use of a Kemmerer type
sampler is recommended for samples collected from depths of greater
than 5 feet.
4.3 When a Kemmerer sampler is used, the BOD sample bottle should be filled
to overflowing. (Overflow for approximately 10 seconds). Outlet tube
of Kemmerer should be inserted to bottom of BOD bottle. Care must be
taken to prevent turbulence and the formation of bubbles when filling
bottle.
4.4 The sample temperature should be recorded at time of sampling as pre-
cisely as required.
54
-------
(Dissolved Oxygen)
4.5 Do not delay the determination of dissolved oxygen in samples having
an appreciable iodine demand or containing ferrous.iron. If samples
must be preserved either method 4.5.1 or 4.5.2, below, may be employed.
4.5.1 Add 2 ml of manganous sulfate reagent and then 2 ml of alkali
azide reagent to the sample contained in the'BOD bottle. Both
reagents must be added well below the surface of the liquid.
Stopper the bottle immediately and mix the contents thoroughly.
The sample should be stored at the temperature of the collection
water, or water sealed and kept at a temperature of 10 to 20°C,
in the dark.
4.5.2 Add 0.7 ml of concentrated H SO, and 1 ml sodium azide solution
(2 g NaN, in 100 ml distilled water) to the sample in the DO
bottle. Store sample as in 4.5.1. Complete the procedure using
2 ml of manganous sulfate solution, 3 ml alkali iodide solution,
and 2 ml of concentrated HJ5Q..
4.6 If either preservation technique is employed, complete the analysis
within 4-8 hours after sampling.
5. Apparatus
5.1 Sample bottles - 300 ml ±3 ml capacity BOD incubation bottles with
tapered ground glass pointed stoppers and flared mouths.
5.2 Pipets - with elongated tips capable of delivering 2.0 ml ±0.1 ml of
reagent.
6. Reagents
6.1 Manganous sulfate solution: Dissolve 480 g manganous sulfate
(MnS0..4H 0) in distilled water and dilute to 1 liter.
55
-------
(Dissolved Oxygen)
6.1.1 Alternately, use 400 g of MnS04-2H20 or 364 g of MnS04.H_0
per liter. When uncertainty exists regarding the water of
crystallization, a solution of equivalent strength may be
obtained by adjusting the specific gravity of the solution to
1.270 at 20°C.
6.2 Alkaline iodide solution: Dissolve 500 g of sodium hydroxide (NaOH)
or 700 g of potassium hydroxide (KOH) and 135 g of sodium iodide (Nal)
or 150 g of potassium iodide (KI) in distilled water and dilute to 1
liter. To this solution add 10 g of sodium azide (NaN_) dissolved in
40 ml of distilled water.
6.3 Sulfuric acid, concentrated.
6.4 Starch solution: Prepare an emulsion of 10 g soluble starch in a mortar
or beaker with a small quantity of distilled watejr. Pour this emulsion
into 1 liter of boiling water, allow to boil a few minutes, and let
settle overnight. Use the clear supernate. This solution may be pre-
served by the addition of 5 ml per liter of chloroform and storage in
a 10°C refrigerator.
6.4.1 Dry, powdered starch indicators such as "thyodene" may be used
in place of starch solution.
6.5 Potassium fluoride solution: Dissolve 40 g KF.2H20 in distilled water
and dilute to 100 ml.
6.6 Sodium thiosulfate, stock solution, 0.75 N: Dissolve 186.15 g
Na^S-O .5H_0 in boiled and cooled distilled water and dilute to liter.
£t £ O £•
Preserve by adding 5 ml chloroform.
6.7 Sodium thiosulfate standard titrant, 0.0375 N: Prepare by diluting
50.0 ml of stock solution to 1 liter. Preserve by adding 5 ml of
56
-------
(Dissolved Oxygen)
chloroform. Standard sodium thiosulfate, exactly 0.0375 N is
equivalent to 0.300 mg of DO per 1.00 ml. Standardize with
0.0375 N potassium biiodate.
6.8 Potassium biiodate standard, 0.0375 N: Dissolve 4.873 g potassium
biiodate, previously dried 2 hours at 103°C, in 1.0 liter of dis-
tilled water. Dilute 250 ml to 1.0 liter for 0.0375 N biiodate
solution.
6.9 Standardization of 0.0375 N sodium thiosulfate: Dissolve
approximately 2 g (±1.0 g) KI in 100 to 150 ml distilled water;
add 10 ml of 10% H-SO. followed by 20 ml standard potassium biiodate.
Place in dark for 5 minutes, dilute to 300 ml, and titrate with
the standard sodium thiosulfate to a pale straw color. Add 1-2 ml
starch solution and continue the titration drop by drop until the
blue color disappears. Run in duplicate. Duplicate determinations
should agree within ±0.05 ml.
7. Procedure
7.1 To the sample collected in the BOD incubation bottle, add 2 ml of
the manganous sulfate solution followed by 2 ml of the alkali-
iodide-azide reagent, well below the surface of the liquid; stopper
with care to exclude air bubbles, and mix well by inverting the
bottle several times. When the precipitate settles, leaving a
clear supernatant above the manganese hydroxide floe, shake again.
When settling has produced at least 100 ml of clear supernate,
carefully remove the stopper and immediately add 2.0 ml of cone.
H_SO. (sulfamic acid packets, 3 g may be substituted for H9SO.)^
(1) Kroner, R. C., Longbottom, J. E., Gorman, R., A Comparison of Various
Reagents Proposed for Use in the Winkler Procedure for Dissolved Oxygen,
PHS Water Pollution Surveillance System Applications and Development
Report #12, Water Quality Section, Basic Data Branch, July 1964.
57
-------
(Dissolved Oxygen)
by allowing the acid to run down the neck of the bottle, re-stopper,
and mix by gentle inversion until the iodine is uniformly dis-
tributed throughout the bottle. Complete the analysis within 45
minutes.
7.2 Transfer the entire bottle contents by inversion into a 500-ml
wide mouth Erlenmeyer flask and titrate with 0.0375 N thiosulfate
solution (where problems of stability arise, 0.0375 N phenylarsine
oxide (PAO)may be substituted as titrant) *• ' to a pale straw color.
Add 1-2 ml of starch solution or 0.1 g of powdered indicator and
continue to titrate to the first disappearance of the blue color.
7.3 If ferric iron is present (100 to 200 ppm), add 1.0 ml of KF
solution before acidification.
7.4 Occasionally, a dark brown or black precipitate persists in the
bottle after acidification. This precipitate will dissolve if the
solution is kept for a few minutes longer than usual or, if parti-
cularly persistent, a few more drops of H..SO. will effect disso-
lution .
8. Calculation
8.1 Each ml of 0.0375 sodium thiosulfate titrant is equivalent to 1 mg
DO when the entire bottle contents are titrated.
8.2 If the results are desired in milliliters of oxygen gas per liter
at 0°C and 760 mm pressure, multiply mg/1 DO by 0.698.
8.3 To express the results as percent saturation at 760 mm atmospheric
pressure, the solubility data in Table 218 (Whipple § Whipple
Table, p. 480, Standard Methods, 13th Edition) may be used.
Equations for correcting the solubilities to barometric pressures
other than mean sea level are given below the table.
58
-------
(Dissolved Oxygen)
8.4 The solubility of DO in distilled water at any barometric pressure,
p (mm Hg), temperature, T°C, and saturated vapor pressure, y (mm Hg) ,
for the given T, may be calculated between the temperature of 0° and
30 °C by:
and between 30° and 50°C by:
.1/1 DO . c - a ; ?-827
9. Precision and Accuracy
9.1 Exact data are unavailable on the precision and accuracy of this
technique; however, reproducibility is approximately 0.2 ppm of DO
at the 7.5 ppm level due to equipment tolerances and uncompensated
displacement errors.
59
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DISSOLVED OXYGEN
(Probe Method)
STORE! NO. 00300
1. Scope and Application
1.1 The probe method for dissolved oxygen is recommended for those samples
containing materials which interfere with the modified Winkler procedure
such as sulfite, thiosulfate, polythionate, mercaptans, free chlorine
or hypochlorite, organic substances readily hydrolyzed in alkaline
solutions, free iodine, intense color or turbidity, biological floes, etc.
1.2 The probe method is recommended as a substitute for the modified Winkler
procedure in monitoring of streams, lakes, outfalls, etc., where it is
desired to obtain a continuous record of the dissolved oxygen content of
the water under observation.
1.3 The probe method may be used as a substitute for the modified Winkler
procedure in BOD determinations where it is desired to perform non-
destructive DO measurements on a sample.
1.4 The probe method may be used under any circumstances as a substitute for
the modified Winkler procedure provided that the probe itself is
standardized against the Winkler method on samples free of interfering
materials.
1.5 The electronic readout meter for the output from dissolved oxygen probes
is normally calibrated in convenient scale (0 to 10, 0 to 15, 0 to 20 mg/1
for example) with a sensitivity of approximately 0.05 mg/liter.
2. Summary of Method
2.1 The most common instrumental probes for determination of dissolved oxygen
in water are dependent upon electrochemical reactions. Under steady-
state conditions, the current or potential can be correlated with DO
60
-------
(DO - Probe Method)
concentrations. Interfacial dynamics at the probe-sample interface
are a factor in probe response and a significant degree of inter-
facial turbulence is necessary. For precision performance, turbulence
should be constant.
3. Sample Handling and Preservation
3.1 See 4.1, 4.2, 4.3, 4.4 under Modified Winkler Method.
4. Interferences
4.1 Dissolved organic materials are not known to interfere in the output
from dissolved oxygen probes.
4.2 Dissolved inorganic salts are a factor in the performance of dissolved
oxygen probe.
4.2.1 Probes with membranes respond to partial pressure of oxygen which
in turn is a function of dissolved inorganic salts. Conversion
factors for seawater and brackish waters may be calculated from
dissolved oxygen saturation versus salinity data. Converson
factors for specific inorganic salts may be developed experimentally.
Broad variations in the kinds and concentrations of salts in
samples can make the use of a membrane probe difficult.
4.2,2 The thallium probe requires the presence of salts in concentrations
which provide a minimum conductivity of approximately 200 micromhos.
4.3 Reactive compounds can interfere with the output or the performance of
dissolved oxygen probes.
4.3.1 Reactive gases which pass through the membrane of membrane probes
may interfere. For example, chlorine will depolarize the cathode
and cause a high probe-output. Long-term exposures to chlorine
61
-------
(DO _ probe Method)
will coat the anode with the chloride of the anode metal and
eventually desensitize the probe. Alkaline samples in which
free chlorine does not exist will not interfere. Hydrogen
sulfide will interfere with membrane probes if the applied
potential is greater than the half-wave potential of the
sulfide ion. If the applied potential is less than the half-
wave potential, an interfering reaction will not occur, but
coating of the anode with the sulfide of the anode metal can • '
take place.
4.3.2 Sulfur compounds (hydrogen sulfide, sulfur dioxide and mer-
captans, for example) cause interfering outputs from the
thallium probe. Halogens do not interfere with the thallium
probe.
4.4 At low dissolved oxygen concentrations, pH variation below pH 5 and
above pH 9 interfere with the performance of the thallium probe
(approximately ±0.05 mg/1 DO per pH unit). The performance of membrane
probes is not affected by pH changes.
4.5 Dissolved oxygen probes are temperature sensitive, and temperature
compensation is normally provided by the manufacturer. The thallium
probe has a temperature coefficient of 1.9 m/°C. Membrane probes have
a temperature coefficient of 4 to 6 percent/°C dependent upon the
membrane employed.
5. Apparatus
5.1 No specific probe or accessory is especially recommended as superior.
However, probes which have been evaluated or are in use and found to be
reliable are the Weston § Stack DO Analyzer Model 30 and the Yellow
Springs Instrument (YSI) Model 54.
62
-------
(DO - Probe Method)
6. Calibration
Follow manufacturer instructions.
7. Procedure
Follow manufacturer instructions.
8. Calculation
Follow manufacturer instructions.
9. Precision and Accuracy
Manufacturer's specification claim 0.1 rag/1 repeatability with ±1% accuracy.
63
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FLUORIDE
(SPADNS Method with Bellack Distillation)
STORE! NO. 00950
1. Scope and Application
1.1 This method is applicable to the measurement of fluoride in
drinking waters, surface waters, domestic wastes and industrial
wastes and saline waters. It is the method to be used when the
accessories for the probe method are not available.
1.2 The method covers the range from 0.1 to about 2.5 mg/1 F.
2. Summary of Method
2.1 Following distillation to remove interferences the sample is
treated with the SPADNS reagent. The loss of color resulting
from the reaction of fluoride with the zirconyl-SPADNS dye is
a function of the fluoride concentration.
3. Comments
3.1 The SPADNS reagent is more tolerant of interfering materials
than other accepted fluoride reagents. Reference to Table 121, (1)
page 169, Standard Method for the Examination of Waters and Waste-
waters, 13th Edition, will help the analyst decide if distillation
is required. The addition of the highly colored SPADNS reagent
must be done with utmost accuracy because the fluoride concen-
tration is measured as a difference of absorbance in the blank
and the sample. A small error in reagent addition is the most
prominent source of error in this test.
4. Precision and Accuracy
4.1 On a sample containing 0.83 mg/1 F with no interferences, 53
analysts using the Bellack distillation and the SPADNS reagent
obtained a mean of 0.81 mg/1 F with a standard deviation of
0.089 mg/1.
64
-------
(Fluoride)
4.2 On a sample containing 0.57 mg/1 F (with 200 mg/1 SO. and
10 mg/1 Al as interferences) 53 analysts using the Bellack
distillation obtained a mean of 0.60 mg F/l with a standard
deviation of 0.103 mg/1.
4.3 On a sample containing 0.68 mg/1 F (with 200 mg/1 SO., 2 mg/1 Al
and 2.5 mg/1 [NaPO_]6 as interferences^ 53 analysts using the
Bellack distillation obtained a mean of 0.72 mg/1 F with a standard
deviation of 0.092 mg/1.
4.4 Analytical Reference Service, Sample 111-B water, Fluoride,
August, 1961.
5. Reference j
The procedure to be used for this determination is found in:
Standard Methods for the Examination of Water and Waste-
waters, pp 171-172 (Method No. 121A, Preliminary Distil-
lation Step) and pp 174-176 (Method 121C, SPADNS) 13th
Edition, (1971).
American Society for Testing and Materials, Part 23, pp
213-218, Method No. D1179-68, (1970).
65
-------
FLUORIDE
(Automated Complexone Method)
;STORET NO. 00950
1. Scope and Application
1.1 This method is applicable to surface waters, domestic and industrial
wastes, and saline waters. The applicable range of the method is
0.05 to 1.5 mg F/l. Twelve samples per hour can be analyzed.
2. Summary of Method
2.1 Fluoride ion reacts with the red cerous chelate of alizarin com~
plexone. It is unlike other fluoride procedures in that a positive
color is developed as contrasted to a bleaching action in previous
methods.
3. Sample Handling and Preservation
3.1 No special requirements.
4. Interferences
4.1 Method is free from most anionic and cationic interferences, except
_3
aluminum, which forms an extremely stable fluoro compound, AlFfi
This is overcome by treatment with 8-hydroxyquinoline to complex
the aluminum and by subsequent extraction with chloroform.
5. Apparatus
5.1 Technicon AutoAnalyzer Unit consisting of:
5.1.1 Sampler I.
5.1.2 Manifold.
5.1.3 Proportioning pump.
5.1.4 Continuous filter.
5.1.5 Colorimeter equipped with 15 mm tabular flow cell and
650 nm filters.
5.1.6 Recorder equipped with range expander.
66
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(Fluoride)
6. Reagents
6.1 Sodium acetate solution: Dissolve 272 g (2 moles) of sodium acetate
in distilled water and dilute to 1 liter.
6.2 Acetic acid-8-hydroxyquinoline solution: Dissolve 6 g of 8-hydroxy-
quinoline in 34 ml of cone, acetic acid, and dilute to 1 liter.
6.3 Chloroform: Analytical reagent grade.
6.4 Ammonium acetate solution (6.7%): Dissolve 67 g of ammonium acetate
in distilled water and dilute to 1 liter.
6.5 Hydrochloric acid (2 N): Dilute 172 ml of cone. HC1 to 1 liter.
6.6 Lanthanum alizarin fluoride blue solution*: Dissolve 0.18 g of
alizarin fluoride blue in a solution containing 0.5 ml of cone.
ammonium hydroxide and 15 ml of 6.7% ammonium acetate. Add a solution
that contains 41 g of anhydrous sodium carbonate and 70 ml of glacial
acetic acid in 300 ml of distilled water. Add 250 ml of acetone.
Dissolve 0.2 g of lanthanum oxide in 12.5 ml of 2 N hydrochloric acid
and mix with above solution. Dilute to 1 liter.
6.7 Stock Solution: Dissolve 2.210 g of sodium fluoride in 100 ml of
distilled water and dilute to 1 liter. 1 ml = 1.0 mg F.
6.8 Standard Solution: Dilute 10.0 ml of stock solution to 1 liter.
1 ml = 0.01 mg F.
6.8.1 Using standard solution, prepare the following standards
in 100-ml volumetric flasks:
M. T. Baker Laboratory Chemical No. J112 or equivalent,
67
-------
(Fluoride)
mg F/l ml Standard Solution/100 ml
0.05 0.5
0.10 1.0
0.20 2.0
0.40 4.0
0.60 6.0
0.80 8.0
1.00 10.0
1.20 12.0
1.50 15.0
7. Procedure
7.1 Set up manifold as shown in Figure 1.
7.2 Allow both colorimeter and recorder to warm up for 30 minutes. Run
a baseline with all reagents, feeding distilled water through the
sample line. Adjust dark current and operative opening on colorimeter
to obtain stable baseline.
7.3 Place distilled water wash tubes in alternate openings in Sampler and
set sample timing at 2.5 minutes.
7.4 Arrange fluoride standards in Sampler in order of decreasing concen-
tration. Complete loading of Sampler tray with unknown samples.
7.5 Switch sample line from distilled water to Sampler and begin analysis.
8. Calculation
8.1 Prepare standard curve by plotting peak heights of processed fluoride
standards against concentration values. Compute concentration of
samples by comparing sample peak heights with standard curve.
9. Precision and Accuracy
9.1 In a single laboratory, using surface water samples at concentrations
of 0.06, 0.15, 0.55, and 1.08 mg F/l, the standard deviation was
±0.018 (AQC Laboratory).
68
-------
(Fluoride)
9.2 In a single laboratory, using surface water samples at concentrations
of 0.14 and 1.25 mg F/l recoveries were 89% and 102%, respectively
(AQC Laboratory)I
References
1. R. Greenhaigh and J. P. Riley, "The Determination of Fluorides in Natural
Waters, with Particular Reference to Sea Water." Anal. Chim. Acta, 25,
179 (1961).
2. K. M. Chan and J. P. Riley, "The Automatic Determination of Fluoride in
Sea Water and Other Natural Waters." Anal. Chim. Acta, 35, 365 (1966).
69
-------
i
LARG
COIL
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FIGURE 1. FLUORIDE MANIFOLD
-------
FLUORIDE
(Specific Ion Electrode Method) STORET No: Total 00951
Dissolved 00950
1. Scope and Application
1.1 This method is applicable to the measurement of fluoride in finished
waters, natural waters, brines, and industrial waste waters and the
need for distillation of the sample is eliminated.
1.2 Concentrations of fluoride from 0.1 up to 1000 mg/liter may be measured.
2. Summary of Method
2.1 The fluoride is determined potentiometrically using a specific ion
fluroide electrode in conjunction with a standard single junction sleeve-
type reference electrode and a pH meter having an expanded millivolt
scale or a specific ion meter having a direct concentration scale for
j
fluoride.
2.2 The fluoride electrode consists of a lanthanum fluoride crystal across
which a potential is developed by fluoride ions. The cell may be re-
presented by Ag/Ag Cl, Cl~ (0.3), F~ (0.001) LaF_/ test solution/SCE/.
o
3. Interferences
3.1 Extremes of pH interfere; sample pH should be between 5 and 9. Poly-
valent cations of Si , Fe and Al interfere by forming complexes
with fluoride. The degree of interference depends upon the concentration
of the complexing cations, the concentration of fluoride and the pH of
the sample. The addition of a pH 5.0 buffer (described below) contain-
ing a strong, chelating agent preferentially complexes aluminum (the
most common interference), silicon, and iron, and eliminates the pH
problem.
4, Sampling Handling and Preservation
4.1 No special requirements.
72
-------
(Fluoride)
5. Apparatus
5.1 Electrometer, (pH meter) with expanded mv scale or a specific ion
meter such as the Orion 400 Series.
5.2 Fluoride Ion Activity Electrode, such as Orion No. 94-09*- ' .
5.3 Reference electrode, single junction, sleeve-type, such as Orion
No. 90-01, Beckman No. 40454, or Corning No. 476010.
5.4 Magnetic Mixer, Teflon-coated stirring bar.
6. Reagents
6.1 Buffer solution, pH 5.0-5.5. To approximately 500 ml of distilled
water in a one-liter beaker add 57 ml of glacial acetic acid, 58 g
of sodium chloride and 2 g of CDTA . Stir to dissolve and cool
to room temperature. Adjust pH of solution to between 5.0 and 5.5
with 5 N sodium hydroxide (about 150 ml will be required). Transfer
solution to a one-liter volumetric flask and dilute to the mark with
distilled water. For work with brines, additional NaCl should be
added to raise the chloride level to twice the highest expected
level of chloride in the sample.
Note - CDTA replaces citric acid used in the original buffer for-
mula. It is a strong chelating agent and more effectively ties up
aluminum than the original citric acid.
6.2 Sodium fluoride, stock solution (1.0 mg = 0.01 mg F). Dissolve
0.2210 g of sodium fluoride in water and dilute to 1.0 liter.
Dilute 100 ml of this solution to 1.0 liter with water. Store
in chemical-resistant glass or polyethylene.
(1) Patent No. 3,431,182 (March 4, 1969).
(2) CDTA is the abbreviated designation of 1,2-cyclohexylene dinitrilo
tetraacetic acid, (Mathieson, Coleman § Bell, Cat. No. P8661) or
cyclohexane diamine tetraacetic acid (Merck-Titriplex IV or Baker
Cat. No. G083).
73
-------
(Fluoride)
7. Calibration
7.1 Prepare a series of standards using the fluoride stock solution
(1 ml = 0.01 mg F) in the range of 0 to 2.00 mg/liter by diluting
appropriate volumes to 50 ml. The following series may be used:
Milliliters of Stock Concentration when Diluted
(1.0 ml = 0.01 mg/F) to 50 ml, mg F/liter
0.00 0.00
1.00 0.20
2.00 0.40
3.00 0.60
4.00 0.80
5.00 1.00
6.00 1.20
8.00 1.60
10.00 2.00
7.2 Calibration of Electrometer: Immerse the electrodes in each stock
solution starting with the lowest concentration and measure the
developed potential while mixing. The electrodes must remain in
the solution for at least three minutes or until the reading has
stabilized. Using semilogarithmic graph paper, plot the concen-
tration of fluoride in mg/liter on the log axis vs. the electrode
potential developed in the standard on the linear axis, starting
with the lowest concentration at the bottom of the scale.
7.3 Calibration of a specific ion meter: Follow the directions of the
manufacturer for the operation of the instrument.
8. Procedure
8.1 Place 50.0 ml of sample and 50.0 ml of buffer in a 150-ml beaker.
Place on a magnetic stirrer and mix at medium speed. Immerse the
electrodes in the solution and observe the meter reading while mixing.
The electrodes must remain in the solution for at least three minutes
74
-------
(Fluoride)
or until the reading has stabilized. At concentrations under 0.5 mg/
liter F, it may require as long as five minutes to reach a stable meter
reading; higher concentrations stabilize more quickly. If a pH meter
is used, record the potential measurement for each unknown sample and
convert the potential reading to the fluoride ion concentration of the
unknown using the standard curve. If a specific ion meter is used,
read the fluoride level in the unknown sample directly in mg/1 on the
fluoride scale.
9. Precision and Accuracy
9.1 A synthetic sample prepared by the Analytical Reference Service, PHS,
containing 0.85 mg/1 fluoride and no interferences was analyzed by 111
different analysts; a mean of 0.84 mg/1 with a standard deviation of
±0.030 was obtained.
9.2 On the same study, a synthetic sample containing 0.75 mg/1 fluoride,
2.5 mg/1 polyphosphate and 300 mg/1 alkalinity, was analyzed by the
same 111 analysts; a mean of 0.75 mg/1 fluoride with a standard deviation
of ±0.036 was obtained.
75
-------
HARDNESS
STORET Number: 00900
1. Scope and Application
1.1 This method is applicable to drinking waters and surface waters,
domestic and industrial wastes.
1.2 The method is suitable for all concentration ranges of hardness;
however, in order to avoid large titration volumes, use a sample
aliquot containing not more than 25 mg CaCO_ per 50 ml sample.
«J . •
1.3 Automated titration may be used.
2. Summary of Method
2.1 Calcium and magnesium ions in the sample are sequestered upon the
addition of disodium dihydrogen ethylenediamine tetraacetate
(Na2EDTA). The end point of the reaction is detected by means of
Chrome Black T or Calmagite/- ' which has a red color in the
presence of calcium and magnesium and a blue color when the cations
are sequestered.
3. Comments
3.1 Excessive amounts of heavy metals can interfere. This is usually
overcome by complexing the metals with cyanide.
3.1.1 Routine addition of sodium cyanide solution (CAUTION: Deadly
poison) to prevent potential metallic interference is
recommended.
4. Precision and Accuracy
4.1 Forty-three analysts in nineteen laboratories analyzed six
synthetic water samples containing exact increments of calcium
and magnesium salts, with the following results:
^ %ach Cat. No. 825 or equivalent.
76
-------
(Hardness)
Increment as
Total Hardness
mg/liter as CaCO,
31
33
182
194
417
444
Precision as
Standard Deviation
mg/liter as CaCO,
2.87
2.52
4.87
2.98
9.65
8.73
Accuracy as
Bias,
-0.87
-0.73
-0.19
-1.04
-3.35
-3.23
Bias ,
mg/liter, CaC03
-0.003
-0.24
0.4
-2.0
-13.0
-14.3
(FWPCA Method Study 1, Mineral and Physical Analyses)
4.2 In a single laboratory (AQC), using surface water samples at an
average concentration of 194 mg CaCO /I, the standard deviation was
O
± 3.
5. Reference
5.1 The procedure to be used for this determination is found in:
Standard Methods for the Examination of Water and Wastewater,
13th Edition, p. 179, Method 122B (1971).
ASTM Standards, Part 23, Water; Atmospheric Analysis, p. 187,
Method D1126-67 (1970).
77
-------
HARDNESS, TOTAL
(Automated Method)
STORET NO. 00900
1. Scope and Application
1.1 This automated method is applicable to surface and saline waters.
The applicable range is 10 to 400 mg/1 as CaCO_. Approximately 12
samples per hour can be analyzed.
2. Summary of Method
2.1 The disodium magnesium EDTA exchanges magnesium on an equivalent
basis for any calcium and/or other cations to form a more stable
EDTA chelate than magnesium. The free magnesium reacts with cal-
magite at a pH of 10 to give a red-violet complex. Thus, by
I
measuring only magnesium concentration in the final reaction stream,
an accurate measurement of total hardness is possible.
3. Sample Handling and Preservation
3.1 No special requirements.
4. Interferences
4.1 No significant interferences.
5. Apparatus
5.1 Technicon AutoAnalyzer consisting of:
5.1.1 Sampler I.
5.1.2 Continuous Filter.
5.1.3 Manifold.
5.1.4 Proportioning Pump.
5.1.5 Colorimeter equipped with 15 mm tubular flow cell and 520
nm filters.
5.1.6 Recorder equipped with range expander.
78
-------
(Hardness, Total)
6. Reagents
6.1 Buffer: Dissolve 67.6 g NH.C1 in 572 ml of NH.OH and dilute to 1 liter.
6.2 Calmagite^•': Dissolve 0.25 g in 500 ml of distilled water by stirring
approximately 30 minutes on a magnetic stirrer. Filter.
6.3 Magnesium EDTA: Dissolve 0.2 g of MgEDTA in 1 liter of distilled water.
6.4 Stock Solution: Weigh 1.0 g of calcium carbonate (pre-dried at 105°C)
into 500 ml Erlenmeyer flask; add 1:1 HC1 until all CaCO_ has dissolved.
o
Add 200 ml of distilled water and boil for a few minutes. Cool, add a
few drops of methyl red indicator, and adjust to the orange color with
3N NH.OH and dilute to 1 liter. 1.0 ml = 1.0 mg CaCO,.
^ o
6.4.1 Dilute each of the following volumes of stock solutions to 250 ml
for appropriate standards:
Stock Solution, ml CaCO,, mg/1
2.5 10.0
5.0 20.0
10.0 40.0
15.0 60.0
25.0 100
35.0 140
50.0 200
75.0 300
100.0 400
7. Procedure
7.1 Set up manifold as shown in Figure 1.
7.2 Allow both colorimeter and recorder to warm up for 30 minutes. Run a
baseline with all reagents, feeding distilled water through the sample
line. Adjust dark current and operative opening on colorimeter to
obtain stable baseline.
Cat. No. 825 or equivalent.
79
-------
(Hardness, Total)
7.3 Place distilled water wash tubes in alternate openings in Sampler
and set sample timing at 2.5 minutes.
7.4 Arrange working standards in Sampler in order of decreasing con-
centration. Complete loading of Sampler tray with unknown samples.
7.5 Switch sample line from distilled water to Sampler and begin analysis,
8. Calculation
8.1 Prepare standard curve by plotting peak heights of processed stan-
dards against concentration values. Compute concentration of
samples by comparing sample peak heights with standard curve.
9. Precision and Accuracy
9.1 In a single laboratory (AQC), using surface water samples at con-
centrations of 19, 120, 385, and 366 mg/1 as CaCO_, the standard
deviations were ±1.5, ±1.5, ±4.5, and ±5.0, respectively.
9.2 In a single laboratory (AQC), using surface water samples at
concentrations of 39 and 296 mg/1 as CaCO,, recoveries were 89%
O
and 93%, respectively.
References
1. Technicon AutoAnalyzer Methodology, Bulletin No. 2, Technicon Controls,
Inc., Chauncey, New York (July 1960).
2. Standard Methods for the Examination of Water and Wastewater, 13th
Edition, p. 179, Method 122B (1971).
80
-------
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FIGURE 1. HARDNESS MANIFOLD
-------
METALS
(Atomic Absorption Methods)
1. Scope and Application
1.1 Metals in solution may be readily determined by atomic absorption
spectroscopy. The method is simple, rapid, and applicable to a
large number of metals in surface waters, domestic and industrial
wastes, and saline waters.
1.2 Detection limits, sensitivity and optimum ranges of the metals
will vary with the various makes and models of satisfactory atomic
absorption spectrophotometers. The data shown in Table 1, however,
provide some indication of the concentration ranges measurable. In
the majority of instances the concentration range shown in the table
may be extended much lower with scale expansion and conversely ex-
tended upwards by using a less sensitive wavelength. Detection
limits may also be extended through concentration of the sample or
through solvent extraction techniques. Table 1 lists detection
limits, sensitivities, and the optimum concentration ranges achieved
directly on the sample using the Instrumentation Laboratories,
Model IL-153 without scale expansion (Pos 2.5). The boat tech-
nique developed at Perkin-Elmer for use with the PE303 or 403 may
also be used to extend absolute detection limits. ^
83
-------
(Metals)
TABLE 1
Concentration Ranges
Optimum
Concentration
Metal
Aluminum
Arsenic
Cadmium
Calcium
Chromium
Copper
Iron
Lead
Magnesium
Manganese
Potassium
Silver
Sodium
Zinc
Detection Limit
mg/1
0.1
0.05
0.001
0.003
0.01
0.005
0.004
0.01
0.0005
0.005
0.005
0.01
0.001
0.005
Sensitivity
mg/1
0.4
1.0
0.004
0.07
0.02
0.04
0.006
0.06
0.005
0.04
0.01
0.05
0.003
0.02
Range
mg/1
10
10
0.1
1
1
0.1
0.1
1
0.01
0.1
0.01
0.1
1
0.1
1000
100
2
200
200
10
20
10
2
20
2
20
200
2
2. Summary of Method
2.1 Atomic absorption spectroscopy is similar to flame emission photometry
in that a sample is atomized and aspirated into a flame. Flame
photometry, however, measures the amount of light emitted, whereas,
in atomic absorption spectrophotometry a light beam is directed
through the flame into a monochromator, and onto a detector that
measures the amount of light absorbed. In many instances absorption
is more sensitive because it depends upon the presence of free un-
excited atoms and generally the ratio of unexcited to excited atoms
at a given moment is very high. Since the wavelength of the light beam
is characteristic of only the metal being determined, the light energy
absorbed by the flame is a measure of the concentration of that metal in
the sample. This principle is the basis of atomic absorption spectroscopy.
2.2 Although methods have been reported for the analysis of solids by
r 2")
atomic absorption spectroscopy the technique generally is limited
84
-------
(Metals)
to metals in solution or solubilized through some form of sample
processing. Thus, it is a relatively simple matter to determine
metals in the dissolved fraction by aspirating a filtered portion
of the water sample.
2.2.1 In those instances where complete characterization of a
sample is desired, the suspended material must also be
analyzed. This may be accomplished by filtration and acid
digestion of the suspended material. Metallic constituents
in this acid digest are subsequently determined and the sum
of the dissolved plus suspended concentrations will then
provide the total concentrations present.
2.2.2 The sample may also be treated with acid before filtration
to measure what may be termed "extractable" concentrations.
3. Definition of Terms
3.1 Sensitivity: is the concentration in milligrams of metal per liter
that produces an absorption of 1%.
3.2 Detection Limit: is defined as the concentration that produces
absorption equivalent to twice the magnitude of the fluctuation in
the background (zero absorption).
3.3 Dissolved Metals: those constituents (metals) which will pass
through a 0.45 n membrane filter.
3.4 Suspended Metals: those constituents (metals) which are retained
by a 0.45 y membrane filter.
3.5 Total Metals: the concentration of metals determined on an unfiltered
sample following vigorous digestion (Section 4.1.3), or the sum of
the concentrations of metals in both the dissolved and suspended
fractions.
85
-------
(Metals)
3.6 Extractable Metals: the concentration of metals in an unfiltered
sample following digestion with hot dilute mineral acid (Section
4.1.4).
4. Sample Handling and Preservation
4.1 For the determination of trace metals, contamination and loss are
of prime concern. Dust in the laboratory environment, impurities
in reagents and impurities on laboratory apparatus which the sample
contacts are all sources of potential contamination. For liquid
samples, containers can introduce either positive or negative errors
in the measurement of trace metals by (a) contributing contaminants
through leaching or surface desorption and (b) by depleting concen-
trations through adsorption. Thus the collection and treatment of
the sample prior to analysis requires particular attention. The
sample bottle should be thoroughly washed with detergent and tap
water; rinsed with chromic acid, tap water, 1:1 nitric acid, tap
water and finally distilled water in that order. Before collection
of the sample a decision must be made as to the type of data desired,
i.e., dissolved, suspended, total or extractable.
4.1.1 For the determination of dissolved constituents the sample should
be filtered through a 0.45 \i membrane filter as soon as
practicable after collection. Use the first 50-100 ml to rinse
the filter flask. Discard this portion and collect the re-
quired volume of filtrate. Acidify the filtrate with 1:1 re-
distilled HNO, (3 ml per liter). Normally this amount of acid
will lower the pH to 2 or 3 and should be sufficient to
preserve the sample indefinitely. (See Note 1). Analyses
performed on a sample so treated shall be reported as "dissolved"
86
-------
(Metals)
concentrations.
NOTE 1: It has been suggested (International Biological
Program, Symposium on Analytical Methods, Amsterdam, Oct.
1966) that additional acid, as much as 25 ml of concentrated
HCl/liter may be required to stabilize certain types of
highly buffered samples if .they are to be stored for any
length of time. Therefore, special precautions should be
observed for preservation and storage of unusual samples in-
tended for trace metal analysis.
4.1.2 For the determination of suspended metals a representative
volume of sample should be filtered through a 0.45 u membrane
filter. When considerable sediment is present, as little as
100 ml of a well shaken sample is filtered.
Record the volume filtered and transfer the membrane filter
containing the sediment to a 250 ml Griffin beaker and add
3 ml distilled HNO_. Cover the beaker with a watch glass and
heat gently. The warm acid will soon dissolve the membrane.
Increase the temperature of the hot-plate and digest the
material. When the acid has evaporated, cool the beaker and
watch glass and add another 3 ml of distilled HNO_.
Cover and continue heating until the digestion is complete,
generally indicated by a light colored residue. Add distilled
1:1 HC1 (2 ml) to the dry residue and again warm the beaker
gently to dissolve the material. Wash down the watch glass
and beaker walls with distilled water and filter the sample
to remove silicates and other insoluble material that could
clog the atomizer. Adjust the volume to some predetermined
value based on the expected concentrations of trace metals
87
-------
(Metals)
present. This volume will vary depending on the metal to
be determined. The sample is now ready for analysis. Con-
centrations so determined shall be reported as "suspended".
STORET parameter numbers for reporting this type of data are
currently being assigned.
4.1.3 For the determination of total metals the sample is not
filtered before processing. Choose a volume of sample
appropriate for the expected level of metals. If much sus-
pended material is present, as little as 50-100 ml of well
mixed sample will most probably be sufficient. (The sample
volume required may also vary proportionally with the
number of metals to be determined).
Transfer a representative aliquot of the well mixed sample to
a Griffin beaker and add 3 ml of concentrated distilled HNO_.
Place the beaker on a hot plate and evaporate to dryness making
certain that the sample does not boil. Cool the beaker and
add another 3 ml portion of distilled concentrated HNO_. Cover
•3
the beaker with a watch glass and return to the hot plate.
Increase the temperature of the hot plate so that a gentle
reflux action occurs. Continue heating, adding additional
acid as necessary until the digestion is complete, generally
indicated by a light colored residue. Add sufficient
distilled 1:1 HC1 and again warm the beaker to dissolve the
residue. Wash down the beaker walls and watch glass with
distilled water and filter the sample to remove silicates and
other insoluble material that could clog the atomizer. Adjust
88
-------
(Metals)
the volume to some predetermined value based on the expected
metal concentrations. The sample is now ready for analysis.
Concentrations so determined shall be reported as "total".
STORET parameter numbers for reporting this type of data have
been assigned and are given for each metal.
4.1.4 To determine metals soluble in diluted hot HC1 - HNO_,
acidify the entire sample at the time of collection with re-
distilled HNO_, 5 ml/1. At the time of analysis the sample
is mixed and a 100-ml aliquot transferred to a beaker or flask.
Five ml of redistilled hydrochloric acid is added and the
sample heated for 15 minutes on a steam bath or hot plate.
After this digestion period the sample is filtered and the
volume adjusted to 100 ml. The sample is then ready for
analysis.
The data so obtained are significant in terms of "total" metals
in the sample, with the reservation that something less than
"total" is actually measured. Concentrations of metal found,
especially in heavily silted samples, will be substantially
higher than data obtained on only the soluble fraction. STORET
parameter numbers for the storage of this type data are not
available at this time.
5. Interferences
5.1 The most troublesome type of interference in atomic absorption spectro-
photometry is usually termed "chemical" and is caused by lack of
absorption of atoms bound in molecular combination in the flame. This
phenomenon can occur when the flame is not sufficiently hot to
89
-------
(Metals)
dissociate the molecule, as in the case of phosphate interference
with magnesium, or because the dissociated atom is immediately
oxidized to a compound that will not dissociate further at the
temperature of the flame. The addition of lanthanum will overcome
the phosphate interference in the magnesium determination. Similarly,
silica interference in the determination of manganese can be
eliminated by the addition of calcium.
5.1.1 Chemical interferences may also be eliminated by separating
the metal from the interfering material. While complexing
agents are usually employed to increase the sensitivity of
the analysis they may also be used to eliminate or reduce
interferences.
6. Apparatus
6.1 Atomic absorption spectrophotometer: Any commercial atomic absorption
instrument having an energy source, an atomizer burner system, a mono-
chromater, and a detector is suitable.
6.2 Burner: A Doling burner is recommended for most aqueous solutions.
A premix burner is used for organic solvents. For certain elements
the nitrous oxide burner is required.
6.3 Volumetric flasks; 200 ml, for extraction with organic solvents.
6.4 Glassware: All glassware, including sample bottles, should be washed
with detergent, rinsed with tap water, chromic acid, tap water, 1:1
nitric acid, tap water and distilled water in that order.
6.5 Borosilicate glass distillation apparatus.
90
-------
(Metals)
7. Reagents
7.1 Deionized distilled water: Prepare by passing distilled water
through a mixed bed of cation and anion exchange resins. Use
deionized distilled water for the preparation of all reagents,
calibration standards, and as dilution water.
7.2 Nitric acid (cone): Distill reagent grade nitric acid in a boro-
silicate glass distillation apparatus. Prepare a 1:1 dilution
with deionized distilled water. Caution: Distillation should be
performed in hood with protective sash in place.
7.3 Hydrochloric acid (1:1): Prepare a 1:1 solution of reagent grade
hydrochloric acid and distilled water. Distill this mixture from
i
j
a borosilicate glas£ distillation apparatus.
7.4 Stock metal solutions: Prepare as directed in 8.1 and under the
individual metal procedures.
7.5 Standard metal solutions: Prepare a series of standards of the metal
by dilution of the appropriate stock metal solution to cover the con-
centration range desired.
7.6 Fuel and oxidant: Commercial grade acetylene is generally acceptable.
Air may be supplied from a compressed air line, a laboratory com-
pressor, or from a cylinder of compressed air. Reagent grade nitrous
oxide is also required for certain determinations.
7.7 Special reagents for the extraction procedure.
7.7.1 Ammonium pyrrolidine dithiocarbamate solution (APDC): Dissolve
1 g APDC in 100 ml of deionized distilled water. Prepare fresh
before use.
7.7.2 Hydrochloric acid, 0.3N: Mix 25 ml cone. HC1 with deionized
distilled water and dilute to 1 liter.
Ammonium pyrrolidine dithiocarbamate (APDC) may be obtained commercially
from Fisher Scientific Company (Cat. No. A-182), K and K Labs., Inc., or
Eastman Kodak.
91
-------
(Metals)
7.7.3 Methyl isobutyl ketone (MIBK): (see Note 2)
NOTE 2: One objection to MIBK is the increased solubility
in a highly acid medium. By using a 3:1 mixture of MIBK -
cyclohexane the solubility in the aqueous phase is decreased
without any significant change in the extraction of the
various chelates or burning characteristics of the ketone.
Ethyl propionate has also been found to be a suitable
solvent. Benzene and kerosene are inferior to MIBK because
they produce a large luminous and smoke flame. Carbon
tetrachloride or chloroform may also be used; however, the
enhancement is considerable less than with MIBK.
7.7.4 Sodium hydroxide, 2.5N: Dissolve 10 g NaOH in deionized
distilled water and dilute to 100 ml.
8. Preparation of Standards and Calibration
8.1 Stock solutions are prepared from high purity metals, oxides or
nonhygroscopic reagent grade salts using redistilled nitric or
hydrochloric acids. Sulfuric or phosphoric acids should be avoided
as they produce an adverse effect on many elements. The stock
solutions are prepared at concentrations of 1000 mg of the metal
per liter.
8.2 Standard solutions are prepared by diluting the stock metal solutions
at the time of analysis. For best results, calibration standards
should be prepared fresh each time an analysis is to be made and
92
-------
(Metals)
discarded after use. Prepare a blank and calibration standards
in graduated amounts in the appropriate range. As the filtered
samples are preserved with redistilled nitric acid (3 ml 1:1 per
liter) the acid strength of the calibration standards should be
similarly adjusted. Beginning with the blank and working toward the
highest standard, aspirate the solutions and record the readings.
Repeat the operation with both the calibration standards and the
samples a sufficient number of times to secure a reliable average
reading for each solution.
8.3 For those instruments which do not read out directly in concentration
a calibration curve is prepared to cover the appropriate concentration
range. Usually, this means the preparation of standards which produce
an absorption of 0 to 80 percent. The correct method for plotting
data derived from an atomic absorption instrument equipped with a
linear readout system is to convert percent absorption to absorbance
and plot the absorbance against concentration. The following relation-
ship is used to convert absorption values to absorbance:
absorbance = log (100/% T) = 2 - log % T
where % T = 100 - % absorption
As the curves are frequently nonlinear, especially at high absorption
values, the number of standards should be increased in that portion
of the curve.
9. General Procedure for Analysis by Atomic Absorption
9.1 Differences between the models of satisfactory atomic absorption
spectrophotometers prevent the formulation of detailed instructions
applicable to every instrument. The analyst should follow the
93
-------
(Metals)
manufacturer's operating instructions for his particular instrument.
In general, after choosing the correct hollow cathode lamp for the
analysis, the lamp should be allowed to warm up for a minimum of
15 minutes. During this period, align the instrument, position the
monochromator at the correct wavelength, select the proper mono-
chromator slit width, adjust the hollow cathode current according to
the manufacturer's recommendation, light the flame and regulate the
flow of fuel and oxidant, adjust the burner for maximum percent
absorption and stability and balance the photometer. Run a series of
standards of the element under analysis and construct working curves
by plotting the concentrations of the standards against the absor-
bance. For those instruments which read directly in concentration
set the curve corrector to read out the proper concentration.
Aspirate the samples and determine the concentrations either
directly or from the calibration curve. For best results run
standards each time a sample or series of samples are run.
9.2 Special Extraction Procedure: When the concentration of the metal
is not sufficiently high to determine directly, or when considerable
dissolved solids are present in the sample, certain of the metals may
be chelated and extracted with organic solvents. Ammonium pyrrolidine
dithiocarbamate (APDC) is widely used for this purpose and is parti-
cularly useful for zinc, cadmium, iron, manganese, copper, silver,
lead and chromium"1"^. Tri-valent chromium does not react with APDC
unless it has first been converted to the hexavalent form . Aluminum,
beryllium, barium and strontium also do not react with APDC.
94
-------
(Metals)
The most frequently used organic solvent for APDC is methyl iso-
butyl ketone (MIBK). Apart from the fact that the solvent should
extract the chelate, it should burn and provide a stable flame.
In addition, the physical properties of the solvent such as vis-
cosity, surface tension, boiling point, and mutual solubility in
an aqueous medium must be taken into account. It should not
produce toxic products during combustion or give a high background
in the flame (see Note 3).
NOTE 3: The methods described herein have been found to be satis-
factory for natural and fresh water types of samples when used by
a qualified analyst. Occasions have been reported when other types
of samples (sea water, brine, etc.) have presented some problems
with the extraction procedure. Therefore, users are cautioned to
confirm their suitability through application on spiked samples.
9.2.1 Extraction Procedure with APDC: The following extraction
procedure is a general one which may be used for the majority
of metals. Manganese, however, will not be extracted unless
the pH is adjusted to between 4.5 and 5.0. In addition, the
manganese complex is extremely unstable and must be analyzed
without delay.
a. Transfer a volume of sample (100 ml maximum) into a 250
ml Griffin beaker and adjust the volume to 100 ml with
deionized distilled water.
b. Prepare a blank and sufficient standards in the same
manner and adjust the volume of each to approximately
100 ml with deionized distilled water.
95
-------
(Metals)
c. Adjust the pH of the samples and standards to a pH of
2.5 using a pH meter.
d. Transfer the samples and standards to a 200 ml volumetric
flask and add 2.5 ml fresh APDC solution and mix.
e. Add 10.0 ml MIBK and shake vigorously for one minute.
f. Allow the layers to separate and add deionized distilled
water until the ketone layer is completely in the neck
of the flask. Centrifuge if separation is not complete.
g. Aspirate the ketone layer and record the scale readings
for each standard and sample against the prepared blank.
Repeat and average the duplicate results. Plot a cali-
bration curve in yg metal vs. absorbance (see Note 4).
NOTE 4: When aspirating organic solvents the fuel-to-
air ratio should be reduced as the burning of the organic
solvent contributes to the fuel supply. When adjusting
the fuel-to-air ratio of the gas mixture at the burner,
begin with the settings recommended by the manufacturer.
Gradually reduce the fuel flow while the organic solvent
is being aspirated until the flame is as blue as possible.
Care should be taken that the flame does not lift off
the burner producing an undesirable luminescent flame.
10. Calculation
10.1 Direct determination: Read the jnetal value in mg/1 from the cali-
bration curve or directly from the readout system of the instrument.
mg/1 metal in sample = (mg/1 of metal in the aliquot) x D
where D = m* °f aliquot + ml of deionized distilled water
ml of aliquot
96
-------
(Metals)
10.2 Extracted samples: Read the metal value in yg from the extracted
calibration curve or from the readout system of the instrument.
mg/1 metal in sample = Vg metal in aliquot
ml of aliquot
11. Precision and Accuracy
11.1 Three synthetic unknown samples containing varying concentrations
of cadmium, chromium, copper, iron, lead, magnesium, manganese,
silver, and zinc were analyzed in 59 laboratories with the results
indicated in Table 2. (Analytical Reference Service PHS).
! Table 2
I
Precision and Accuracy Data for Atomic Absorption Methods
Metal
Direct determination
Cadmium
Chromium
Copper
Iron
Magnesium
Manganese
Silver
Zinc
Extracted samples
Cadmium
Lead
Metal
Concentration ,
Vg/1
50
50
1000
300
200
50
50
500
10
50
Relative
Error,
percent
8.15
2.29
3.42
0.64
6.30
6.00
10.57
0.41
3.03
19.00
Relative
Standard
Deviation,
percent
21.62
26.44
11.23
16.53
10.49
13.50
17.47
8.15
72.77
23.46
References:
(1) Atomic Absorption Newsletter, 7_, 35 (1968).
(2) Spectrochim Acta, 24B, 53 (1969).
(3) Atomic Absorption Newsletter, 6_, 128 (1967).
97
-------
AUMHHI
(Standard Conditions) DISSOLVED: 01105
TOTAL : 01106
Optimum Concentration Range 10-1000 rag/1 using the 3092 A line
Sensitivity 0.4 mg/1
Detection Limit 0.1 mg/1
Preparation of Standard Solution
1. 'Stock Solution: Carefully weigh 1.000 gram of aluminum metal
(analytical reagent grade). Add 15 ml of concentrated HC1 to the
metal in a covered beaker and warm gently. When solution is complete,
transfer quantitatively to 1 liter volumetric flask and make up to
volume with distilled water. One ml equals 1 mg Al.
2. Prepare dilutions of the stock solution to be used as calibration
standards at the time of analysis. Maintain an acid strength of
0.15% nitric acid in all calibration standards.
Instrumental Parameters (General)
1. Aluminum hollow cathode lamp
2. Wavelength: 3092 A
3. Type of burner: Nitrous oxide
4. Fuel: Acetylene
5. Oxidant: Nitrous oxide
6. Type of flame; Fuel rich
7. Photomultiplier tube: IP-28
Notes
1. The following lines may also be used:
3082 A Relative Sensitivity 1
3962 A Relative Sensitivity 2
3944 A Relative Sensitivity 2.5
98
-------
ARSENIC
,„.,,_,.. . STORE! NO:
(Standard Conditions) DISSOLVED: 01000
TOTAL : 01QQ2
Optimum Concentration Range 10-100 mg/1 using the 1937 A line
Sensitivity 1.0 mg/1
Detection Limit 0.5 mg/1
Preparation of Standard Solution
1. Stock Solution: Dissolve 1.320 grams of arsenic trioxide (As^O ,
analytical reagent grade) in a small quantity of distilled water
in which a pellet of NaOH has previously been dissolved. When solution
is complete acidify with HC1 and make up to 1 liter with distilled
water. One ml equals 1 mg As (1000 mg/1).
I
2. Prepare dilutions of the stock solution to be used as calibration
standards at the time of analysis.
Instrumental Parameters (General)
1. Arsenic hollow cathode lamp
2. Wavelength: 1937 A
3. Type of burner: Nitrous oxide
4. Fuel: Acetylene
5. Oxidant: Nitrous oxide
6. Type of flame: Fuel rich
7. Photomultiplier tube: R-106
Notes
1. The R-106 photomultiplier tube is more sensitive to UV light and
therefore is suggested in place of the IP-28 phototube.
2. Arsenic may also be determined using an air-acetylene system; however,
the detection limit is 3-5 mg/1. Using an argon-hydrogen system this
limit may be lowered to 0.25 mg/1; however, both chloride a'nd nitrate
ions interfere.
99
-------
(Metals)
3. Samples high in total salt content (above 1%) will produce an
apparent absorption at the 1937 A arsenic line even when the
element is absent using the air-acetylene system.
4. The high-solids burner is reported to give lower detection limits
with both the argon-hydrogen and air-acetylene systems.
5. The silver diethyldithiocarbamate colorimetric method is suggested
for low levels of arsenic.
100
-------
CADMIUM
STORE! NO:
(Standard Conditions) DISSOLVED: 01025
TOTAL : 01027
Optimum Concentration Range 0.1-1 mg/1 using the 2288 A line
Sensitivity 0.004 mg/1
Detection Limit 0.001 mg/1
Preparation of Standard Solution
1. Stock Solution: Carefully weigh 1.142 grams of cadmium oxide
(CdO, analytical reagent' grade) and dissolve in 5 ml redistilled
HNO_. Dilute to 1 liter with distilled water. One ml equals
1 mg Cd.
2. Prepare dilutions of the stock solution to be used as calibration
standards at the time of analysis. Maintain an acid strength of
0.15% nitric acid in all calibration standards.
Instrumental Parameters (General)
1. Cadmium hollow cathode lamp
2. Wavelength: 2288 A
3. Type of burner: Boling
4. Fuel: Acetylene
5. Oxidant: Air
6. Type of flame: Oxidizing
7. Photomultiplier tube: IP-28
101
-------
CALCIUM STORE! NO: Total 00916
(Standard Conditions) Dissolved 00915
Optimum Concentration Range 1.0-200 mg/1 using the 4227 A line
Sensitivity 0.07 mg/1
Detection Limit 0.003 mg/1
Preparation of Standard Solution
1. Stock Solution: Suspend 1.250 grams of CaCO_ (analytical reagent
O
grade), dried at 180°C for 1 hour before weighing, in distilled
water and dissolve cautiously with a minimum of dilute HC1. Dilute
to 1000 ml with distilled water. One ml equals 0.5 mg of Ca
(500 mg/1).
2. Lanthanum chloride solution: Dissolve 29 g of La 0_, slowly and in
2 5
small portions, in 250 ml concentrated HC1. (Caution! Reaction is
violent) and dilute to 500 ml with distilled water.
3. Prepare dilutions of the stock calcium solutions to be used as cali-
bration standards at the time of analysis. To each calibration
standard solution, add 1.0 ml of LaCl_ solution for each 10 ml of
volume of working standard, ie., 20 ml working standard + 2 ml
LaCl_ = 22 ml.
Instrumental Parameters (General)
1. Calcium hollow cathode lamp
2. Wavelength: 4227 A
3. Type of burner: Boling
4. Fuel: Acetylene
5. Oxidant: Air
6. Type of flame: Reducing
7. Photomultiplier tube: IP-28
102
-------
(Metals)
Notes
1. Phosphate, sulfate and aluminum interfere but are masked by the
addition of lanthanum. Since low calcium values result if the pH
of the sample is above 7, both standards and samples are prepared
in dilute hydrochloric acid solution. Concentrations of magnesium
greater than 1000 mg/1 also cause low calcium values. Concentrations
of up to 500 mg/1 each of sodium, potassium and nitrate cause no inter-
ference .
2. Anionic chemical interferences can be expected if lanthanum is not
used in samples and standards.
3. The nitrous oxide-acetylene flame will provide two to five times
|.
greater sensitivity and freedom from chemical interferences. lonization
interferences should be controlled by adding a large amount of alkali
to the samples and standards. The analysis appears to be free from
chemical supressions in the nitrous oxide - acetylene flame.
4. The 2399 A line may also be used. This line has a sensitivity of
20 mg/1.
103
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CHROMIUM
STORET NO:
(Standard Conditions) DISSOLVED: 01030
TOTAL : 01054
Optimum Concentration Range 1.0-200 mg/1 using the 3579 A line
Sensitivity 0.02 mg/1
Detection Limit 0.01 mg/1
Preparation of Standard Solution
1. Stock Solution: Dissolve 1.923 gram of chromium trioxide (CrO_,
O
reagent grade) in distilled water. When solution is complete,
acidify with redistilled HNO_ and dilute to 1 liter with distilled
water. One ml equals 1 mg chromium.
2. Prepare dilutions of the stock solution to be used as calibration
standards at the time of analysis. Maintain an acid strength of
0.15% nitric acid in all calibration standards.
Instrumental Parameters (General)
1. Chromium hollow cathode lamp
2. Wavelength: 3579 A
3. Type of burner: Boling
4. Fuel: Acetylene
5. Oxidant: Air
6. Type of flame: Slightly fuel rich
7. Photomultiplier tube: IP-28
Notes
1. The following wavelengths may also be used:
3605 A Relative Sensitivity 1.2
3593 A Relative Sensitivity 1.4
4254 A Relative Sensitivity 2
4274 A Relative Sensitivity 3
4289 A Relative Sensitivity 4
104
-------
(Metals)
2. The determination of chromium requires a rich acetylene flame.
The absorption is very sensitive to the fuel-to-air ratio.
3. The absorption of chromium is suppressed by iron and nickel. If
the analysis is performed in a lean flame the interference can
be lessened but the sensitivity will also be reduced. The inter-
ference does not exist in a nitrous oxide - acetylene flame.
4. For low levels of chromium the extraction procedure (MIBK-APDC) is
recommended. Only hexavalent chromium will react with APDC, thus,
to measure trivalent chromium an oxidation step must be included.
(See ref. 3).
105
-------
COPPER STORET NO:
CStandard Conditions) DISSOLVED: 01040
TOTAL : 01042
Optimum Concentration Range 0.1-10 mg/1 using the 3247 A line
Sensitivity 0.04 mg/1
Detection Limit 0.005 mg/1
Preparation of Standard Solution
1. Stock Solution: Carefully weigh 1.00 gram of electrolytic copper
(analytical reagent grade). Dissolve in 5 ml redistilled HNO, and
make up to 1 liter with distilled water. Final concentration is 1
mg Cu per ml (1000 mg/1).
2. Prepare dilutions of the stock solution to be used as calibration
standards at the time of analysis. Maintain an acid strength of
0.15% nitric acid in all calibration standards.
Instrumental Parameters (General)
1. Copper hollow cathode lamp
2. Wavelength: 3247 A
3. Type of burner: Boling
4. Fuel: Acetylene
5. Oxidant: Air
6. Type of flame: Oxidizing
7. Photomultiplier tube: IP-28
Notes
1. For copper concentrations below 0.05 mg/1, the extraction procedure
is suggested.
2. Copper atoms are distributed over a wider area in laminar flow-flames
than that normally found. Consequently, the burner parameters are not
as critical as for most other elemental determinations.
106
-------
(Metals)
3. Because of the spectral intensity of the 3247 A line, the P.M. tube
may become saturated. If this situation occurs the current should
be decreased.
4. Numerous absorption lines are available for the determination of
copper. By selecting a suitable absorption wavelength, copper samples
may be analyzed over a very wide range of concentration. The following
lines may be used:
3264 A Relative Sensitivity 2
2178 A Relative Sensitivity 4
2165 A Relative Sensitivity 7
2181 A Relative Sensitivity 9
i,
2225 A Relative Sensitivity 20
2024 A Relative Sensitivity 20
2492 A Relative Sensitivity 90
107
-------
STORET NO:
(Standard Conditions) DISSOLVED: 01046
TOTAL : 01045
Optimum Concentration Range 0.1-20 mg/1 using the 2483 A line
Sensitivity 0.006 mg/1
Detection Limit 0.004 mg/1
Preparation of Standard Solution
1. Stock Solution: Carefully weigh 1.000 gram of pure iron wire
(analytical reagent grade) and dissolve in 5 ml redistilled
HNO_, warming if necessary. When solution is complete make up
to 1 liter with distilled water. One ml equals 1 mg Fe (1000 mg/1).
2. Prepare dilutions of the stock solutions to be used as calibration
standards at the time of analysis. Maintain an acid strength of
0.15% nitric acid in all calibration standards.
Instrumental Parameters (General)
1. Iron hollow cathode lamp
2. Wavelength: 2483 A
3. Type of burner: Boling
4. Fuel: Acetylene
5. Oxidant: Air
6. Type of flame: Oxidizing
7. Photomultiplier tube: IP-28
Notes
1. The following lines may also be used:
2488 A Relative Sensitivity 2
2522 A Relative Sensitivity 2
2719 A Relative Sensitivity 4
3021 A Relative Sensitivity 5
108
-------
(Metals)
2527 A Relative Sensitivity 6
2721 A Relative Sensitivity 9
3720 A Relative Sensitivity 10
2967 A Relative Sensitivity 12
3860 A Relative Sensitivity 20
3441 A Relative Sensitivity 30
2. Absorption is strongly dependent upon the lamp current.
3. Better signal-to-noise can be obtained from a neon-filled hollow
cathode lamp than from an argon-filled lamp.
109
-------
LEAD
(Standard Conditions) S™?ED: 01049
TOTAL : 01051
Optimum Concentration Range 1-10 mg/1 using the 2170 A line
Sensitivity 0.06 mg/1
Detection Limit 0.01 mg/1
Preparation of Standard Solution
1. Stock Solution: Carefully weigh 1.599 gram of analytical reagent
grade lead nitrate [Pb(NO_)2,;} and dissolve in redistilled water.
When solution is complete acidify with 10 ml redistilled HNO_ and
dilute to 1 liter with distilled water. One ml equals 1 mg Pb
(1000 mg/1).
2. Prepare dilutions of the stock solution to be used as calibration
standards at the time of analysis. Maintain an acid strength of
0.15% nitric acid in all calibration standards.
Instrumental Parameters (General)
1. Lead hollow cathode lamp
2. Wavelength: 2170
3. Type of burner: Boling
4. Fuel: Acetylene
5. Oxidant: Air
6. Type of flame: Slightly oxidizing
7. Photomultiplier tube: IP-28
Notes
1. The analysis of this metal is exceptionally sensitive to turbulence
and absorption bands in the flame. Therefore, some care should be
taken to position the light beam in the most stable, center portion of
110
-------
(Metals)
the flame. To do this, first adjust the burner to maximize the
absorbance reading with a lead standard. Then, aspirate a water
blank and make minute adjustments in the burner alignment to
minimize the signal.
2. Better analytical results with the 2170 A line may be obtained by
using a R-106 photomultiplier tube which is more sensitive to UV
light.
3. For lead concentrations below 0.2 mg/1, the extraction procedure
is suggested. The optimum pH for the extraction is 2.8.
4. The following lines may also be used:
2833 A Relative Sensitivity 2
|
2614 A Relative Sensitivity 500
3683 A Relative Sensitivity 900
111
-------
MAGNESIUM STQRET NQ.
(Standard Conditions) DISSOLVED: 00925
TOTAL : 00927
Optimum Concentration Range 0.01-2 mg/1 using the 2852 A line
Sensitivity 0.005 mg/1
Detection Limit 0.0005 mg/1
Preparation of Standard Solution
1. Stock Solution: Dissolve 0.829 g of magnesium oxide, MgO
(analytical reagent grade) in 10 ml of redistilled HNO, and
dilute to 1 liter with distilled water. One ml equals 0.50 mg.
2. Lanthanum chloride solution: Dissolve 29 g of La?0_, slowly
f» O
and in small portions in 250 ml concentrated HC1, (Caution!
Reaction is violent) and dilute to 500 ml with distilled water.
3. Prepare dilutions of the stock magnesium solution to be used as
calibration standards at the time of analysis. To each calibration
standard solution, add 1.0 ml of LaCl, solution for each 10 ml
O
of volume of working standard, ie., 20 ml working standard + 2 ml
LaCl3 = 22 ml.
Instrumental Parameters (General)
1. Magnesium hollow cathode lamp
2. Wavelength: 2852 A
3. Type of burner: Boling
4. Fuel: Acetylene
5. Oxidant: Air
6. Type of flame: Reducing
7. Photomultiplier tube: IP-28
Notes
1. Analytical sensitivity decreases with increased lamp current.
2. The interference caused by aluminum at concentrations greater than
112
-------
(Metals)
2 mg/1 is masked by addition of lanthanum. Since low magnesium
values result if the pH of the samples is above 7, both standards
and samples are prepared in dilute hydrochloric acid. Sodium,
potassium and calcium cause no interference at concentrations less
than 400 mg/1.
3. Because of the spectral intensity of the 2852 line, the P.M. tube
may become saturated. If this situation occurs, the current should
be decreased.
4. The f&llowing lines may also be used:
2025 A Relative Sensitivity 250
7025 A Relative Sensitivity 250
2796 A Relative Sensitivity 1000
5. To cover the range of magnesium values normally observed in surface
waters (0.1-20 mg/1), it is suggested that the burner be rotated 55s
113
-------
MANGANESE
STORET NO:
(Standard Conditions) DISSOLVED; 01056
TOTAL : 01055
Optimum Concentration Range 0.1-20 mg/1 using the 2795 A line
Sensitivity 0.04 mg/1
Detection Limit 0.005 mg/1
Preparation of Standard Solution
1. Stock Solution: Carefully weigh 1.583 gram of analytical reagent
grade manganese dioxide, MnO and dissolve in 10 ml of HC1. When
solution is complete dilute to 1 liter with distilled water. One
ml equals 1 mg Mn (1000 mg/1).
2. Prepare dilutions of the stock solution to be used as calibration
standards at the time of analysis. Maintain an acid strength of
0.15% nitric acid in all calibration standards.
Instrumental Parameters (General)
1. Manganese hollow cathode lamp
2. Wavelength: 2795 A
3. Type of burner: Boling
4. Fuel: Acetylene
5. Oxidant: Air
6. Type of flame: Oxidizing
7. Photomultiplier tube: IP-28
Notes^
1. For manganese concentrations below 0.01 mg/1, the extraction
procedure is suggested. The extraction is carried out at pH 4.5-5.
The manganese chelate is very unstable and the analysis must be
made without delay to prevent its re-solution in the aqueous phase.
2. Analytical sensitivity is somewhat dependent on lamp current.
114
-------
POTASSIUM
(Stanza Coitions, S™™D:
TOTAL : 00957
Optimum Concentration Range 0.01-2 mg/1 using the 7665 A line
Sensitivity 0.01 mg/1
Detection Limit 0.005 mg/1
Preparation of Standard Solutions
1. Stock Solution: Dissolve 0.1907 grains of KC1 (analytical reagent
grade), dried at 110°C, in distilled water and make up to 1 liter.
One ml equals 0.10 mg of potassium (100 mg/1).
2. Prepare dilutions of the stock solution to be used as calibration
standards at the time of analysis.
Instrumental Parameters (General)
j :
1. Potassium hollow cathode lamp
2. Wavelength: 7665 A
3. Type of burner: Boling
4. Fuel: Acetylene
5. Oxidant: Air
6. Type of flame: Slightly oxidizing
7. Photomultiplier tube: IP-21
Notes
1. If an IP-21 photodetector tube is not available, the IP-28 may be
used. This will result in some loss of sensitivity.
2. The Osram potassium vapor-discharge lamp may also be used in the
Perkin-Elmer 303." In this case the lamp current should be 350 ma or
the optimum operating current.
3. Sodium may interfere if present at much higher levels than the
potassium. This effect can be avoided by approximately matching the
115
-------
(Metals)
sodium content of the potassium standards with that of the sample.
4. Potassium absorption is enhanced in the presence of Na, Li and Cs,
especially in a high-temperature flame. This enhancement effect of
sodium can be eliminated by changing the burner height and the type
of flame used. The burner assembly is set approximately 0.05 cm below
the optical light path so that the optical light path is sliced at the
bottom by the burner head. A fuel-rich flame is used (303-burner,
airflow 7.5, acetylene flow 9.0).
5. The 4044 A line may also be used. This line has a sensitivity of
5 mg/1 for 1% absorption.
6. To cover the range of potassium values normally observed in surface
waters (0.1-20 mg/1), it is suggested that the burner be rotated 75°.
116
-------
SILVER
(Standard Conditions) ^DISSOLVED: 01075
TOTAL : 01077
Optimum Concentration Range 0.1-20 mg/1 using the 3281 A line
Sensitivity 0.05 mg/1
Detection Limit 0.01 mg/1
Preparation of Standard Solution
1. Stock Solution: Dissolve 1.575 g of AgNO_ (analytical reagent grade)
in distilled water, add 10 ml HNO, and make up to 1 liter. One ml
equals 1 mg of silver (1000 mg/1).
2. Prepare dilutions of the stock solution to be used as calibration
standards at the time of analysis. Maintain an acid strength of
0.15% HNO_ in all calibration standards.
Instrumental Parameter (General)
1
1. Silver hollow cathode lamp
2. Wavelength: 3281 A
3. Type of burner: Doling
4. Fuel: Acetylene
5. Oxidant: Air
6. Type of flame: Oxidizing
7. Photomultiplier tube: IP-28
Notes
1. The 3382 A line may also be used. This line has a relative
sensitivity of 3.
2. Silver nitrate standards are light sensitive. Dilutions of the
stock should be discarded after use as concentrations below 10 mg/1
are not stable over long periods of storage.
117
-------
SODIUM
S™: 00930
TOTAL : 00929
Optimum Concentration Range 1.0-200 mg/1 using the 3302 A line
Sensitivity 0.003 mg/1
Detection Limit 0.001 mg/1
Preparation of Standard Solutions
1. Stock Solution: Dissolve 2.542 g of NaCl (analytical reagent grade),
dried at 140°C, in distilled water and make up to 1 liter. One ml
equals 1 mg of sodium (1000 mg/1) .
2. Prepare dilutions of the stock solution to be used as calibration
standards at the time of analysis.
Instrumental Parameters (General)
1. Sodium hollow cathode lamp
2. Wavelength: 3302 A
3. Type of burner: Boling
4. Fuel: Acetylene
5 . Oxidant : Air
6. Type of flame: Oxidizing
7. Photomultiplier tube: IP- 28
Notes
1. For the Perkin-Elmer instrument the "290" burner is used to
increase the concentration range of sodium using the most sensitive
line 5890. The burner is installed perpendicular (rotated 90°)
to the light path. The upper concentration limit is 60 mg/1 without
sample dilution.
2. The 3302 A resonance line of sodium yields a sensitivity of about
5 mg/1 sodium for 1% absorption and provides a convenient way to
118
-------
avoid the need to dilute more concentrated solutions of sodium.
3. Low-temperature flames increase sensitivity by reducing the extent
of ionization of this easily ionized metal.
4. For more sensitivity the IP-21 photomultiplier tube and the 5890 A
line may be used to extend the range to 0.005-0.2 mg/1.
119
-------
ZINC
,_. . , ,, ,._ . STORE! NO:
(Standard Conditions) DISSOLVED: 01090
TOTAL : 01092
Optimum Concentration Range 0.1-2 mg/1 using the 2139 A line
Sensitivity 0.02 mg/1
Detection Limit 0.005 mg/1
Preparation of Standard Solution
1. Stock Solution: Carefully weigh 1.00 gram of analytical reagent
grade zinc metal and dissolve cautiously in 10 ml HNO_. When
solution is complete make up to 1 liter with distilled water. One
ml equals 1 mg Zn (1000 mg/1).
2. Prepare dilutions of the stock solution to be used as calibration
standards at the time of analysis. Maintain an acid strength of
0.15% HNO, in all calibration standards.
Instrumental Parameters (General)
1. Zinc hollow cathode lamp
2. Wavelength: 2139 A
3. Type of burner: Boling
4. Fuel: Acetylene
5. Oxidant: Air
6. Type of flame: Oxidizing
7. Photomultiplier tube: IP-28
Notes
1. High levels of silicon may interfere.
2. The air-acetylene flame absorbs about 25% of the energy at the
2139 A line.
3. The sensitivity may be increased by the use of low-temperature flames.
120
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MERCURY
(Flameless AA Procedure)
STORE! NO.
Total: 71900
Dissolved: 71890
1. Scope and Application
1.1 This method is applicable to surface waters, saline waters, waste-
waters and effluents.
1.2 With proper digestion other materials such as fish tissue, mud and
sediments may also be analyzed using the described technique (see
Appendix 11.1 and 11.2).
1.3 In addition to inorganic forms of mercury, organic mercurials may
also be present in an effluent or surface water sample. These organo-
!
mercury compounds will not respond to the flameless atomic absorption
i .
technique unless they are first broken down and converted to mercuric
ions. Potassium permanganate oxidizes many of these compounds but
recent studies have shown that a number of organic mercurials, in-
cluding phenyl mercuric acetate and methyl mercuric chloride, are only
partially oxidized by this method.
Potassium persulfate has been found to give approximately 100% recovery
when used as the oxidant with these compounds. Therefore, a persulfate
oxidation step following the addition of the permanganate has been
included to insure that organo-mercury compounds, if present, will be
oxidized to the mercuric ion before measurement.
1.4 The range of the method may be varied through instrument and/or recorder
expansion. Using a 100 ml sample, a detection limit of 0.2 yg Hg/1
can be achieved; concentrations below this level should be reported
as <0.2 (see Appendix 11.4).
121
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2. Summary of Method
2.1 The flameless AA procedure is a physical method based on the absorption
of radiation at 253.7 nm by mercury vapor. The mercury is
reduced to the elemental state and aerated from solution in a closed
system. The mercury vapor passes through a cell positioned in the
light path of an atomic absorption spectrophotometer. Absorbance
(peak height) is measured as a function of mercury concentration and
recorded in the usual manner.
3. Sample Handling and Preservation
3.1 Until more conclusive data are obtained, samples should be preserved
by acidification with nitric acid to a pH of 2 or lower immediately
at the time of collection . If only dissolved mercury is to be
determined, the sample should be filtered before the acid is added.
For total mercury the filtration is omitted.
4. Interference
4.1 Possible interference from sulfide is eliminated by the addition of
potassium permanganate. Concentrations as high as 20 mg/1 of sulfide
as sodium sulfide do not interfere with the recovery of added in-
organic mercury from distilled water.
4.2 Copper has also been reported to interfere; however, copper concen-
trations as high as 10 mg/1 had no effect on the recovery of mercury
from spiked samples.
4.3 Sea waters, brines and industrial effluents high in chlorides require
additional permanganate (as much as 25 ml). During the oxidation
step chlorides are converted to free chlorine which will also absorb
radiation at 253 nm. Care must be taken to assure that free chlorine
is absent before the mercury is reduced and swept into the cell. This
may be accomplished by using an excess of hydroxylamine sulfate
122
-------
reagent (25 ml). In addition, the dead air space in the BOD bottle
must be purged before the addition of stannous sulfate. Both in-
organic and organic mercury spikes have been quantitatively recovered
from sea water using this technique.
4.4 Interference from certain volatile organic materials which will
absorb at this wavelength is also possible. A preliminary run with-
out reagents should determine if this type of interference is present
(see Appendix 11.3).
5. Apparatus
5.1 Atomic Absorption Spectrophotometer*: Any atomic absorption unit
having an open sample presentation area in which to mount the
absorption cell is suitable. Instrument settings recommended by the
i ^
particular manufacturer should be followed.
5.2 Mercury Hollow Cathode Lamp: Westinghouse WL - 22847, argon filled,
or equivalent.
5.3 Recorder: Any multi-range variable speed recorder that is compatible
with the UV detection system is suitable.
5.4 Absorption Cell: Standard spectrophotometer cells 10 cm long, having
quartz end windows may be used. Suitable cells may be constructed from
plexiglass tubing, 1" O.D. x 4-1/2". The ends are ground perpendicular
to the longitudinal axis and quartz windows (1" diameter x 1/16"
thickness) are cemented in place. Gas inlet and outlet ports (also
of plexiglass but 1/4" O.D.) are attached approximately 1/2" from
each end. The cell is strapped to a burner for support and aligned
in the light beam by use of two 2" by 2" cards. One inch diameter
*Instruments designed specifically for the measurement of mercury using
the cold vapor technique are commercially available and may be substituted
for the atomic absorption spectrophotometer.
123
-------
holes are cut in the middle of each card; the cards are then placed
over each end of the cell. The cell is then positioned and adjusted
vertically and horizontally to give the maximum transmittance.
5.5 Air Pump: Any peristaltic pump capable of delivering 1 liter of air
per minute may be used. A Masterflex pump with electronic speed
control has been found to be satisfactory.
5.6 Flowmeter: Capable of measuring an air flow of 1 liter per minute.
5.7 Aeration Tubing: A straight glass frit having a coarse porosity.
Tygon tubing is used for passage of the mercury vapor from the sample
bottle to the absorption cell and return.
5.8 Drying Tube: 6" x 3/4" diameter tube containing 20 grams of magnesium
perchlorate (see Note 1.) The apparatus is assembled as shown in the
accompanying diagram.
NOTE 1: In place of the magnesium perchlorate drying tube, a small
reading lamp with 60W bulb may be used to prevent condensation of
moisture inside the cell. The lamp is positioned to shine on the
absorption cell maintaining the air temperature in the cell about
10°C above ambient.
6. Reagents
6.1 Sulfuric Acid, Cone: Reagent grade
6.1.1 Sulfuric acid, 1.0 N: Dilute 28.0 ml of cone, sulfuric acid
to 1.0 liter.
6.1.2 Sulfuric acid, 0.5 N: Dilute 14.0 ml of cone, sulfuric acid
to 1.0 liter.
6.2 Nitric Acid, Cone: Reagent grade of low mercury content.
NOTE 2: If a high reagent blank is obtained, it may be necessary to
distill the nitric acid.
124
-------
6.3 Stannous Sulfate: Add 25 g stannous sulfate to 250 ml of 0.5 N
sulfuric acid. This mixture is a suspension and should be stirred
continuously during use.
NOTE 3: Stannous chloride and hydroxylamine hydrochloride may also
be used.
6.4 Sodium Chloride-Hydroxylamine Sulfate Solution: Dissolve 12 grams
of sodium chloride and 12 grams of hydroxylamine sulfate in distilled
water and dilute to 100.0 ml.
6.5 Potassium Permanganate: 5% solution, w/v. Dissolve 5 grams of
potassium permanganate in 100 ml of distilled water.
6.6 Potassium Persulfate: 5% solution, w/v. Dissolve 5 grams of potassium
persulfate in 100 ml of distilled water.
i •
6.7 Stock Mercury Solution: Dissolve 0.1354 grams of mercuric chloride in
75 ml of distilled water. Add 10 ml of concentrated nitric acid and
adjust the volume to 100.0 ml. 1 ml = 1 mg Hg.
6.8 Working Mercury Solution: Make successive dilutions of the stock
mercury solution to obtain a working standard containing 0.1 yg per
ml. This working standard and the dilutions of the stock mercury
solution should be prepared fresh daily. Acidity of the working
standard should be maintained at 0.15% nitric acid. This acid should
be added to the flask as needed before the addition of the aliquot.
7. Calibration
7.1 Transfer 0, 1.0, 2.0 and 5.0 ml aliquots of the working mercury solution
containing 0 to 0,.5 yg of mercury to a series of 300 ml BOD bottles.
Add enough distilled water to each bottle to make a total volume of
100 ml. Mix thoroughly and add 5 ml of concentrated sulfuric acid
and 2.5 ml of nitric acid to each bottle.
125
-------
NOTE 4: Loss of mercury may occur at elevated temperatures. How-
ever, with the stated amounts of acid the temperature rise is only
13°C (25 -> 38°C) and no losses of mercury were observed.
Add 1 ml of KMnO. solution to each bottle and allow to stand at
least 15 minutes. Add 2 ml of potassium persulfate to each bottle
and allow to stand for at least 30 minutes additional. Add 2 ml of
sodium chloride - hydroxylamine sulfate solution to reduce the excess
permanganate. Treating each bottle individually, add 5 ml of the
stannous sulfate solution and immediately attach the bottle to the
aeration apparatus forming a closed system. At this point the sample
is allowed to stand quietly without manual agitation. The circulating
pump, which has previously been adjusted to a rate of 1 liter per minute,
is allowed to run continuously.
The absorbance will increase and reach maximum within 30 seconds. As
soon as the recorder pen levels off, approximately 1 minute, open the
bypass valve and continue the aeration until the absorbance returns to
its minimum value (see Note 5). Close the bypass valve, remove the
stopper and frit from the BOD bottle and continue the aeration.
Proceed with the standards and construct a standard curve by plotting
peak height versus micrograms of mercury.
NOTE 5: Because of the toxic nature of mercury vapor precaution must
be taken to avoid its inhalation. Therefore, a bypass has been in-
cluded in the system to either vent the mercury vapor into an exhaust
hood or pass the vapor through some absorbing media, such as:
a) equal volumes of 0.1 N KMn04 and 10% H2S04
b) 0.25% iodine in a 3% KI solution
126
-------
A specially treated charcoal that will adsorb mercury vapor is
also available from Barnebey and Cheney, E. 8th Ave. and North
Cassidy St., Columbus, Ohio 43219, Cat. #580-13 or #580-22.
8. Procedure
8.1 Transfer 100 ml or an aliquot diluted to 100 ml containing not more
than 0.5 yg of mercury to a 300 ml BOD bottle. Add 5 ml of sulfuric
acid and 2.5 ml of nitric acid mixing after each addition (see
Note 4 under 7). Add 1 ml of potassium permanganate solution (6.5)
to each sample bottle. Shake and add additional portions of potassium
permanganate solution (6.5) until the purple color persists for at
least 15 minutes. Add 2 ml of potassium persulfate to each bottle
and allow to stand an additional 30 minutes. Add sodium chloride-
hydroxylamine sulfate in 2 ml increments to reduce the excess per-
i '
manganate. Add 5 ml of stannous sulfate and immediately attach the
bottle to the aeration apparatus. Continue as described under
Calibration.
9. Calculation
9.1 Determine the peak height of the unknown from the chart and read the
mercury value from the standard curve.
9.2 Calculate the mercury concentration in the sample by the formula:
ygHg/1 = yg Hg x 1000
in aliquot volume of aliquot
9.3 Report mercury concentrations as follows:
Below 0.2 yg/1, <0.2; between 1 and 10 yg/1, one decimal; above 10 yg/1,
whole numbers.
10. Precision and Accuracy
10.1 Using an Ohio River composite sample with a background mercury con-
centration of 0.35 yg/1, spiked with concentrations of 1, 3 and 4
127
-------
Hg/1, the standard deviations were ±0.14, ±0.10 and ±0.08,
respectively. Standard deviation at the 0.35 level was ±0.16.
Percent recoveries at the three levels were 89, 87, and 87%,
respectively.
11. Appendix
11.1 For the measurement of mercury in fish tissue, the procedure of
(21
Uthe, Armstrong, and Stainton^ ' was found to be satisfactory. The
digestion step is carried out directly in the BOD bottle. After the
potassium permanganate oxidation step, the volume of the digest is
adjusted to approximately 100 ml with distilled water and the same
procedure followed as used for water samples.
11.2 For the analysis of mud and sediment samples a vigorous digestion
using a water cooled reflux condenser approximately 2 feet in length
is used. A 5.0 gram sample is placed in a 250 ml round bottom flask
and fitted to the condenser. Add 10 ml of redistilled nitric acid
and apply heat using a heating mantle until the acid refluxes gently.
Continue heating for 2 hours and cool the mixture. Wash down the
column with about 60 - 70 ml of distilled water. Filter the sample
through Whatman No. 42 paper to remove the insoluble material and make
the filtrate up to 100 ml with distilled water. Take a suitable
aliquot for analysis and proceed as described under the procedure for
water samples. If an aliquot of less than 25 ml is taken for analysis,
additional nitric acid is added to make a total of 2.5 ml.
11.3 While the possibility of absorption from certain organic substances
actually being present in the sample does exist, the AQC Laboratory
has not encountered such samples. This is mentioned only to caution
the analyst of the possibility. A simple correction that may be used
is as follows:
128
-------
If an interference has been found to be present (4.4), the
organic vapor may be removed by bubbling air through the sample
while under oxidizing conditions. Before the hydroxylamine and
stannous sulfate reagents are added, the sample bottle should be
attached to the aeration apparatus and any deviation from a
comparably-treated blank noted. The reductants are then added
and a second reading is made. The true mercury value is then
obtained by subtracting the observed deviation from the blank
from this second reading.
11.4 If additional sensitivity is required, a 200 ml sample with recorder
expansion may be used provided the instrument does not produce
undue noise. Using a Coleman MAS-50 with a drying tube of magnesium
|
perchlorate and a variable recorder, 2 mv was set to read full
scale. With these conditions, and distilled water solutions of
mercuric chloride at concentrations of 0.15, 0.10, 0.05 and
0.025 yg/1 the standard deviations were ±0.027, ±0.006, ±0.01 and ±0.004.
Percent recoveries at these levels were 107, 83, 84 and 96%, respectively.
References
1. Wallace, R.A., Fulkerson, W., Shults, W.D., and Lyon, W.S., "Mercury
in the Environment - The Human Element", Oak Ridge National Laboratory,
ORNL - NSF - EP - 1. January, 1971, Page 31.
2. Uthe, J.F. Armstrong, F.A.J. and Stainton, M.P., "Mercury Determination
in Fish Samples by Wet Digestion and Flameless Atomic Absorption Spectro-
photometry", Jour. Fisheries Research Board of Canada, 27, 805 (1970).
3. Hatch, W.R., and Ott, W.L., "Determination of Sub-Microgram Quantities
of Mercury by Atomic Absorption Spectrophotometry", Anal. Chem. 40,
2085 (1968).
4. Brandenberger, H. and Bader, H., "The Determination of Nanogram Levels of
Mercury in Solution by a Flameless Atomic Absorption Technique", Atomic
Absorption Newsletter, 6_, 101 (1967) .
5. Brandenberger, H. and Bader, H., "The Determination of Mercury by Flameless
Atomic Absorption II. A Static Vapor Method", Atomic Absorption Newsletter,
7, 53 (1968).
129
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SCHEMATIC ARRANGEMENT OF EQUIPMENT FOR MERCURY MEASUREMENT
BY COLD VAPOR AA TECHNIQUE
A - Sample container, approximately 300 ml (BOD bottle)
B - Drying tube, 150-200 ml capacity with MgciO,
C - Rotameter, = 1 liter of air/minute
D - Cell, with quartz windows
E - Air pump, = 1 liter of air/minute
F - Glass tube with fritted end
G - Hollow cathode Hg Lamp
H - AA Detector
J - Gas washing bottle containing 0.25% iodine in a 3% potassium
iodide solution
K - Recorder, any compatible model
130
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METHYLENE BLUE ACTIVE SUBSTANCES (MBAS)
(Methylene Blue Method)
STORET NO. 38260
1. Scope and Application
1.1 This method is applicable to the measurement of methylene blue
active substances (MBAS) in drinking waters, surface waters,
domestic and industrial wastes. It is not applicable to measure-
ment of surfactant-type materials in saline waters.
1.2 It is not possible to differentiate between linear alkyl
sulfonate (LAS) and alkyl benzene sulfonate (ABS) or other isomers
of this type compounds. However, LAS has essentially replaced
ABS on the surfactant market so that measurable surfactant materials
i
i
will probably be LAS type materials.
1.3 The method is applicable over the range of 0.025 to 100 mg/1 LAS.
2. Summary of Method
2.1 The dye, methylene blue, in aqueous solution reacts with anionic-
type surface active materials to form a blue colored salt. The
salt is extractable with chloroform and the intensity of color
produced is proportional to the concentration of MBAS.
3. Comments
3.1 Materials other than man-made surface active agents which react
with methylene blue are organically bound sulfates, sulfonates,
carboxylates, phosphates, phenols, cyanates, thiocyanates and
some inorganic ions such as nitrates and chlorides. However, the
131
-------
(MB AS)
occurrence of these materials at interference levels is
relatively rare and with the exception of chlorides may
generally be disregarded.
3.2 Chlorides at concentration of about 1000 mg/1 show a positive
interference but the degree of interference has not been
quantified. For this reason the method is not applicable to
brine samples.
3.3 Naturally occurring organic materials that react with methylene
blue are relatively insignificant. Except under highly unusual
circumstances, measurements of MBAS in finished waters, surface
waters and domestic sewages may be assumed to be accurate
measurements of man-made surface active agents.
4. Precision and Accuracy
4.1 On a sample of filtered river water, spiked with 2.94 mg LAS/liter,
110 analysts obtained a mean of 2.98 mg liter with a standard
deviation of 0.272.
4.2 On a sample of tap water spiked with 0.48 mg LAS/liter, 110
analysts obtained a mean of 0.49 mg/1 with a standard deviation
of 0.048.
4.3 On a sample of distilled water spiked with 0.27 mg LAS/liter,
110 analysts obtained a mean of 0.24 mg/1 with a standard
deviation of 0.036.
4.4. Analytical Reference Service, Water Surfactant No. 3, Study
No. 32, (1968).
132
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(MBAS)
5. References
The procedure to be used for this determination is found in:
Standard Methods for the Examination of Water and Waste-
waters, 13th Edition, pp 339-342, Method No. 159A (1971).
American Society for Testing and Materials, Part 23,
Method D2330-68, pp 721-727, (1970).
133
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NITROGEN-AMMONIA
(Distillation Procedure)
STORE! NO. 00610
1. Scope and Application
1.1 This distillation method covers the determination of ammonia-nitrogen,
exclusive of total Kjeldahl nitrogen, in surface waters, domestic and
industrial wastes, and saline waters. It is the method of choice where
economics and sample load do not warrant the use of automated equipment.
1.2 The method covers the range from about 0.05 to 1.0 mg/1 NH,/N per liter
for the colorimetric procedures and from 1.0 to 25 mg/1 for the
titrimetric procedure.
1.3 This method is described for macro glassware; however, micro distillation
equipment may also be used.
2. Summary of Method
2.1 The sample is buffered at a pH of 9.5 with a borate buffer in order
to decrease hydrolysis of cyanates and organic nitrogen compounds, and
is then distilled into a solution of boric acid. The ammonia in the
distillate can be determined either colorimetrically by nesslerization
or titrimetrically with standard sulfuric acid with the use of a mixed
indicator, the choice between these two procedures depending on the con-
centration of the ammonia.
3. Sample Handling and Preservation
3.1 Until more conclusive data is obtained samples may be preserved by
addition of 40 mg HgCl- per liter and stored at 4°C. If only ammonia
is to be determined on the sample it may be preserved with 1.0 ml of
concentrated H^SO. per liter and stored at 4°C.
134
-------
(Nitrogen-Ammonia)
4. Interferences
4.1 A number of aromatic and aliphatic amines, as well as other compounds,
both organic and inorganic, will cause turbidity upon the addition of
Nessler reagent, so direct nesslerization (i.e., without distillation),
has been discarded as an official method.
4,2, Cyanate, which may be encountered in certain industrial effluents,
, =will hydrolyze to some extent even at the pH of 9.5 at which distillation
is carried out. Volatile alkaline compounds such as hydrazine will
influence the titrimetric results. Some volatile compounds, such as
.certain ketones, aldehydes, and alcohols, may cause an off-color upon
nesslerization in the distillation method. Some of these, such as
formaldehyde, may be eliminated by boiling off at a low pH (approximately
2 to 3) prior to distillation and nesslerization.
4.3 Residual chlorine must also be removed by pre-treatment of the sample
with sodium thiosulfate before distillation.
4.4 If the sample has been preserved with a mercury salt, the mercury ion
must be complexed with sodium thiosulfate prior to distillation.
5. Apparatus
5.1 An all-glass distilling apparatus with an 800-1000 ml flask.
5.2 Spectrophotometer or filter photometer for use at 425 nm and providing ,
a light path of 1 cm or more.
5.3 Nessler tubes: Matched Nessler tubes (APHA Standard) about 300 mm long,
17 mm inside diameter, and marked at 225 mm ±1.5 mm inside measurement
from bottom.
5.4 Erlenmeyer flasks: The distillate is collected in 500 ml glass-
stoppered flasks. These flasks should be marked at the 350 and the
500 ml volumes. With such marking, it is not necessary to transfer
the distillate to volumetric flasks.
135
-------
(Nitrogen-Ammonia)
6. Reagents
6.1 Distilled water should be free of ammonia. Such water is best
prepared by passage through an ion exchange column containing a
strongly acidic cation exchange resin mixed with a strongly basic
anion exchange resin. Regeneration of the column should be carried
out according to the manufacturer's instructions.
6.2 Ammonium chloride, stock solution, (1.0 ml = 1.00 mg NH,-N). Dissolve
3.819 g NH.C1 in water and bring to volume in a 1 liter volumetric
flask,
6.3 Ammonium chloride, standard solution, (1.0 ml = 0.01 mg). Dilute
10 ml of this stock solution to 1 liter in a volumetric flask for use
as the standard ammonium chloride solution.
6.4 Boric acid solution (20 g/1) - Dissolve 20 g H_BO_ in water and dilute
to 1 liter.
6.5 Mixed indicator - Mix 2 volumes of 0.2 percent methyl red in 95 percent
ethyl alcohol with 1 volume of 0.2 percent methylene blue in 95 percent
ethyl alcohol. This solution should be prepared fresh every 30 days.
Note 1 - Specially denatured ethyl alcohol conforming to Formula 3A
or 30 of the U.S. Bureau of Internal Revenue may be substituted for
95 percent ethanol.
6.6 Nessler reagent - Dissolve 100 g of mercuric iodide and 70 g of
potassium iodide in a small amount of water. Add this mixture slowly,
with stirring, to a cooled solution of 160 g of NaOH in 500 ml of
water. Dilute the mixture to 1 liter. If this reagent is stored in
a Pyrex bottle out of direct sunlight, it will remain stable for a
period of up to 1 year.
136
-------
(Ni trogen-Ammoni a)
Note 2 - This reagent should give the characteristic color with
ammonia within 10 minutes after addition, and should not produce a
precipitate with small amounts of ammonia (0.04 mg in a 50 ml
volume).
6.7 Borate buffer - Add 88 ml of 0.1 N NaOH solution to 500 ml of
0.025 M sodium tetraborate solution (5.0 g Na^B.O- per liter) and
dilute to 1 liter.
6.8 Sulfuric acid, standard solution, (0.02 N, 1 ml = 0.28 mg NH_-N).
O
Prepare a stock solution of approximately 0.1 N acid by diluting
3 ml of concentrated H-SO. (sp. gr. 1.84) to 1 liter with G0_-free
distilled water. Dilute 200 ml of this solution to 1 liter with
(XL-free distilled Water. Standardize the approximately 0.02 N
acid so prepared against 0.0200 N Na?CO, solution. This last solution
is prepared by dissolving 1.060 g anhydrous Na-CO,, oven-dried at
140°C, and diluting to 1 liter with (XL-free distilled water.
Note 3 - An alternate and perhaps preferable method is to standardize
the approximately 0.1 N H?SO. solution against a 0.100 N Na_CO_
solution. By proper dilution the 0.0200 N acid can then be prepared.
6.9 Sodium hydroxide, 1 N. Dissolve 40 g NaOH in ammonia-free water
and dilute to 1 liter.
6.10 Dechlorinating reagents. A number of dechlorinating reagents may
be used to remove residual chlorine prior to distillation. These
include:
(a) Sodium thiosulfate (1/70 N): Dissolve 3.5 g Na2S203 in ammonia-
free water and dilute to 1 liter. One ml of this solution will
remove 1 mg/1 of residual chlorine in 500 ml of sample.
137
-------
(Nitrogen-Ammonia)
(b) Sodium arsenite (1/70 N): Dissolve 1.0 g NaAsCL in ammonia-
free water and dilute to 1 liter.
7. Procedure
7.1 Preparation of equipment - Add 500 ml of ammonia-free water to an
800 ml Kjeldahl flask. The addition of boiling chips which have been
previously treated with dilute NaOH will prevent bumping. Steam out
the distillation apparatus until the distillate shows no trace of
ammonia with Nessler reagent.
7.2 Sample preparation - To 400 ml of sample add 1 N NaOH until the pH
is 9.5, checking the pH during addition with a pH meter or by use of
a short range pH paper.
7.3 Distillation - Transfer the sample, the pH of which has been adjusted
to 9.5, to an 800 ml Kjeldahl flask and add 25 ml of the borate buffer.
Distill 300 ml at the rate of 6-10 ml/min. into 50 ml of 2% boric acid
contained in a 500 ml glass stoppered Erlenmeyer flask. Dilute the
distillate to 500 ml in the flask and nesslerize an aliquot to obtain
an approximate value of the ammonia-nitrogen concentration. For con-
centrations above 1.0 mg/1 the ammonia should be determined titri-
metrically. For concentrations below this value it is determined
colorimetrically.
7.4 Determination of ammonia in distillate - Determine the ammonia content
of the distillate either titrimetrically or colorimetrically as de-
scribed below. (See 7.4.1 and 7.4.2).
7.4.1 Titrimetric determination. Add 3 drops of the mixed indicator
to the distillate and titrate the ammonia with the 0.02 N H2SO ,
matching the end point against a blank containing the same volume
138
-------
(Nitrogen-Ammonia)
uf ammonia-free water and H BO solution.
3 3
7.4.2 Colorimetric determination. Prepare a series of Nessler
tube standards as follows:
ml of Standard Cone., When Diluted to
1.0 ml = 0.01 mg NH3N 50.0 ml, mg NHjN/liter
0.0 (Blank) 0.0
0.2 0.04
0.5 0.10
1.0 0.20
1.5 0.30
2.0 0.40
3.0 0.60
4.0 0.80
Dilute each tube to 50 ml with ammonia-free water, add
1.0 ml of Nessler reagent and mix. After 20 minutes read
I
the optical densities at 425 nm against the blank. From
the values obtained plot optical density (absorbance) vs.
concentration for the standard curve.
7.4.3 It is not imperative that all standards be distilled in the
same manner as the samples. It is recommended that at least
two standards (a high and low) be distilled and compared to
similar values on the curve to insure that the distillation
technique is reliable. If distilled standards do not agree
with undistilled standards the operator should find the cause
of the apparent error before proceeding.
7.5 Determine the ammonia in the distillate by nesslerizing 50 ml or an
aliquot diluted to 50 ml and reading the optical density at 425 nm
as described above for the standards. Ammonia-nitrogen content is
read from the standard curve.
139
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(Nitrogen- Ammonia)
8. Calculations
8.1 Titrimetric
mg/l NH.N =
o
in which :
9.
A X
100°
A = ml 0.02 N H2S04 used
S = ml sample
8.2 Spectrophotometric
/i MU M A x
ng/1 NH3N = -
in which:
078-s
A = NH_N read from standard curve
O
S = volume of distillate nesslerized
Precision and Accuracy
9.1 Twenty- four analysts in sixteen laboratories analyzed natural water
samples containing exact increments of an ammonium salt, with the
following results:
Increment as
Nitrogen, Ammonia
mg N/ liter
.21
.26
1.71
1.92
Precision as
Standard Deviation
mg N/liter
0.122
0.070
0.244
0.279
Accuracy
Bias,
% mg
- 5.54
-18.12
+ 0.46
- 2.01
as
Bias,
N/ Liter
-.01
-.05
+ .01
-.04
(FWPCA Method Study 2, Nutrient Analyses)
140
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NITROGEN, AMMONIA
(Automated Method)
STORE! NO. 00610
1. Scope and Application
1.1 This method pertains to the determination of ammonia present in
surface and saline waters. Depending upon the selection of the size
of flow cell, and extent of dilution, concentrations in the range
between .01 and 2LO mg/liter N present as NH may be determined.
O
2. Summary of Method
2.1 The intensity of the indophenol blue color , formed by the reaction
of ammonia with alkaline phenol hypochlorite, is measured. Sodium
nitroprusside is used to intensify the blue color.
3. Sample Handling and Preservation
3.1 Preservation by addition of 40 mg HgCl9 per liter and refrigeration
I
at 4°C. Note HgCl- interference under 4.3.
4. Interferences
4.1 In sea water, calcium and magnesium ions are present in concentrations
sufficient to cause precipitation problems during the analysis. This
problem is eliminated by using 5% EDTA.
4.2 Any marked variation in acidity or alkalinity among samples should
be eliminated, since the intensity of the color used to quantify the
concentration is pH dependent. Likewise, the pH of the wash water and
the standard ammonia solutions should approximate that of the samples.
For example, if the samples have been preserved with 1 ml concentrated
H2SO./liter, the wash water and standards should also contain 1 ml cone.
H2S04/1.
4.3 Mercury chloride, used as a preservative, gives a negative interference
by complexing with the ammonia. This is overcome by adding a comparable
141
-------
(Nitrogen, Ammonia)
amount of HgCl2 to the ammonia standards used for the preparation
of the standard curve.
5. Apparatus
5.1 Technicon AutoAnalyzer Unit consisting of:
5.1.1 Sampler.
5.1.2 Manifold.
5.1.3 Proportioning pump.
5.1.4 Heating bath with double delay coil.
5.1.5 Colorimeter equipped with 15 mm tubular flow cell and 630
or 650 nm filters.
5.1.6 Recorder.
6. Reagents
6.1 Distilled Water: Special precaution must be taken to insure that
distilled water is free of ammonia. Such water is prepared by passage
of distilled water through an ion exchange column comprised of a
mixture of both strongly acidic cation and strongly basic anion
exchange resins. Since organic contamination may interfere with this
analysis, use of the resin Dowex XE-75 or equivalent which also tends
to remove organic impurities is advised. The regeneration of the ion
exchange column should be carried out according to the instruction
of the manufacturer.
6.2 Segmenting Fluid: Air scrubbed with 5N H-SO.. Ammonia free concen-
trated sulfuric acid and ammonia free distilled water used in the
acid preparation.
6.3 Sodium Phenolate: Using a 1 liter Erlenmeyer flask, dissolve 83 g
phenol in 500 ml distilled water. In small increments, cautiously
add with agitation, 32 g of NaOH. Periodically, cool flask under
water faucet. When cool, dilute to 1 liter.
142
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(Nitrogen, Ammonia)
6.4 Sodium Hypochlorite Solution ("Clorox"): Dilute 250 ml of 5% "Clorox"
to 500 ml with distilled water. Available chlorine level should
approximate 2 to 3%. Since "Clorox" is a proprietary product and its
formulation is subject to change, the analyst must remain alert to
detecting any variation in this product significant to its use in this
procedure.
6.5 EDTA (5%): Dissolve 50 g of EDTA (disodium salt) and approximately
six pellets of NaOH in 1 liter of ammonia-free water.
Note: On salt water samples where EDTA solution does not prevent
precipitation of cations, sodium potassium tartrate solution may be
used to advantage. It is prepared as follows:
I
6.5.1 Sodium Potassium Tartrate Solution: 10% NaKC.H.O,. To 900 ml
i 446
distilled water add 100 g sodium potassium tartrate. Add 2
pellets of NaOH and a few boiling chips, boil gently for 45
minutes. Cover, cool, and dilute to 1 liter. Adjust pH to
5.2 ± .05 with H SO . After allowing to settle overnight in a
£f T1
cool place, filter to remove precipitate. Then add 1/2 ml
*
Brij-35 solution and store in stoppered bottle.
6.6 Sodium Nitroprusside (0.05%): Dissolve 0.5 g of sodium nitroprusside
in 1 liter of ammonia-free water.
6.7 Stock Solution: Dissolve 3.819 g of anhydrous ammonium chloride,
NHLC1, dried at 105°C, in ammonia-free water, and dilute to 1 liter.
1 ml = 1.0 mg NH_N.
- - O
Available from Technicon Corporation.
143
-------
(Nitrogen, Ammonia)
6.8 Standard Solution A: Dilute 10.0 ml of stock solution to 1 liter
with ammonia-free water. 1 ml = .01 mg NH_N.
6.9 Standard Solution B: Dilute 10.0 ml of standard solution A to
100 ml with ammonia-free water. 1 ml = .001 mg NH_N.
6.10 Using standard solutions A and B, prepare the following standards
in 100 ml volumetric flasks (prepare fresh daily):
NH_N, mg/1 ml Standard Solution/100 ml
Solution B
0.01 1.0
0.02 2.0
0.05 5.0
0.10 10.0
Solution A
0.20 2.0
0.50 5.0
0.80 8.0
1.00 10.0
1.50 15.0
2.00 20.0
Note: When saline water samples are analyzed, Substitute Ocean Water
(SOW) should be used for preparing the above standards used for the
calibration curve; otherwise, distilled water is used. If SOW is
used, determine its blank background.
Substitute Ocean Water (SOW)
NaCl
MgCl_
Na~SO .
CaCl2
KC1
,./!.
24.53
5.20
4.09
1.16
0.70
NaHC03
KBr
H3B°3
SrCl2
NaF
g./l.
0.20
0.10
0.03
.03
.003
144
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(Nitrogen, Ammonia)
7. Procedure
7.1 For a working range of 0.01 to 2.00 NH N mg/1, set up the manifold
as shown in Figure 1. Higher concentrations may be accommodated by
decreasing sample size and/or through dilution of sample.
7.2 Allow both colorimeter (with 650 nm filters and 15 mm flow cell) and
recorder to warm up for 30 minutes. Run a baseline with all reagents,
feeding ammonia-free water through sample line. Adjust dark current and
operative opening on colorimeter to obtain stable baseline.
7.3 Place a distilled water wash tube in alternate openings in sampler and
set sample timing at 2.0 minutes. All tubes must be rinsed with
|
j ;
ammonia-free water before use.
i
7.4 Arrange ammonia standards in sampler in order of decreasing concen-
tration of nitrogen. Complete loading of sampler tray with unknown
samples.
7.5 Switch sample line from distilled water to sampler and begin analysis.
8. Calculations
8.1 Prepare appropriate standard curve derived from processing ammonia
standards through manifold. Compute concentration of samples by
comparing sample peak heights with standard curve.
9. Precision and Accuracy
9.1 In a single laboratory (AQC), using surface water samples at con-
centrations of 1.41, 0.77, 0.59, and 0.43 mg NHj-N/1, the standard
deviation was ±0.005.
9.2 In a single laboratory (AQC), using surface water samples at con-
centrations of 0.16 and 1.44 mg NH_-N/1, recoveries were 107% and
99%, respectively.
145
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(Nitrogen, Ammonia)
References
1. D. Van Slyke and A. Killer, "Determination of Ammonia in Blood,"
J. Biol. Chem. 102, 499 (1933).
2. B. O'Connor, R. Dobbs, B. Villiers, and R. Dean, "Laboratory Distillation
of Municipal Waste Effluents," JWPCF 39, R 25 (1967).
3. J. E. O'Brien and J. Fiore, "Ammonia Determination by Automatic Analysis,"
Wastes Engineering 55, 552 (1962).
4. A wetting agent recommended and supplied by the Technicon Corporation
for use in AutoAnalyzers.
5. ASTM "Manual on Industrial Water and Industrial Waste Water," 2nd Ed., 1966
printing, 418.
146
-------
i
SMALL MIXING COIL (Sm)
E MIXING COIL (Lmj '
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Sm
1 1
7o/-Vil HF1TINC Ri
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P
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M
PR
P B
G G
G G
w w
Wiif
ff
R R
P P
ml/min
,2.90 SAMPLE
SAMPLER ife O g
^0.80 5% EDTA Oi?jL
.2.00 FILTERED SAMPLE T3 {
^2.00 AIR* CONTINUOt
40.60 Na PHENOLATE
J.60 NaOCI
0.80 NITROPRUSSIDE
.2.50 WASTE
OPORTIONING PUMP
O
Sm
COLORIMETER
15mm TUBULAR f/c
650 nm FILTERS
IX
RECORDER
SAMPLING TIME',2.0 MINUTES
WASH TUBES: ONE
'SCRUBBED THROUGH 5N H SO
2 4
FIGURE 1. AMMONIA MANIFOLD
-------
NITROGEN KJELDAHL, TOTAL
STORET NO. 00625
1. Scope and Application
1.1 This method covers the determination of total Kjeldahl nitrogen in
surface waters, domestic and industrial wastes, and saline waters.
The procedure converts nitrogen components of biological origin such
as amino acids, proteins and peptides to ammonia, but may not convert
the nitrogenous compounds of some industrial wastes such as amines,
nitro compounds, hydrazones, oximes, semi-carbazones and some re-
fractory tertiary amines.
1.2 Two alternatives are listed for the determination of ammonia after
distillation; the titrimetric method which is applicable to concen-
trations above 1 mg N/liter and the Nesslerization method which is
1
applicable to concentrations below 1 mg N/liter.
1.3 This method is described for a macro system of glassware; however, micro
glassware which does not change the chemistry of the procedure is
equally applicable.
2. Definitions
2.1 Total Kjeldahl is defined as the sum of free ammonia and organic
nitrogen compounds which are converted to ammonium sulfate (NH.)2SO.,
under the conditions of digestion described below.
2.2 Organic Kjeldahl Nitrogen is defined as the difference obtained by
subtracting the free ammonia value (cf Nitrogen, Ammonia, this Manual)
from the total Kjeldahl nitrogen value. This may be determined
directly by removal of ammonia before digestion.
3. Summary of Method
3.1 The sample is heated in the presence of concentrated sulfuric acid,
K9SO. and HgSO. and evaporated until S0_ fumes are obtained and the
^ ^T *T O
149
-------
(Nitrogen Kjeldahl, Total)
solution becomes colorless or pale yellow. The residue is cooled,
diluted, and is treated and made alkaline with a hydroxide-thio-
sulfate solution. The ammonia is distilled and determined after
distillation either by nesslerization or titrimetrically.
4. Sample Handling and Preservation
4.1 Samples may be preserved by addition of 40 mg HgCl_/l and stored at
4°C. Even when so preserved, conversion of organic nitrogen to ammonia
may occur. Preserved samples should be analyzed as soon as possible.
5. Apparatus
5.1 Digestion apparatus. A Kjeldahl digestion apparatus with 800 ml flasks
and suction takeoff to remove SO- fumes and water is required. Use
of micro-Kjeldahl equipment is also permissible.
5.2 Distillation apparatus. The Kjeldahl flask is connected to a condenser
and an adaptor so that the distillate can be collected for nesslerization
or in indicating H_BO, solution for titration.
5.3 Spectrophotometer for use at 400 to 425 nm with a light path of 1 cm or
longer.
5.4 Nessler tubes, tall form 50 ml.
6. Reagents
6.1 Distilled waters should be free of ammonia. Such water is best prepared
by the passage of distilled water through an ion exchange column con-
taining a strongly acidic cation exchange resin mixed with a strongly
basic anion exchange resin. Regeneration of the column should be
carried out according to the manufacturer's instructions.
6.2 Mercuric sulfate solution. Dissolve 8 g red, mercuric oxide (HgO) in
50 ml of 1:5 sulfuric acid and dilute to 100 ml with distilled water.
150
-------
(Nitrogen Kjeldahl, Total)
6.3 Sulfuric acid-mercuric sulfate-potassium sulfate solution. Dissolve
267 g K2S04 in 1300 ml water and add 400 ml concentrated H2SO.. Add
50 ml mercuric sulfate solution and dilute to 2 liters.
6.4 Sodium hydroxide-sodium thiosulfate solution. Dissolve 500 g NaOH and
25 g Na2S203.5H20 in water and dilute to 1 liter.
6.5 Phenolphthalein indicator solution. Dissolve 5 g phenolphthalein in
500 ml 95% ethyl alcohol or isopropanol and add 500 ml water. Add 0.02
NaOH dropwise until a faint, pink color appears.
6.6 Mixed indicator. Mix 2 volumes of 0.2% methyl red in 95% ethanol with
1 volume of 0.2% methylene blue in ethanol. Prepare fresh every 30
days.
6.7 Boric acid solution. Dissolve 20 g boric acid, H B0_, in water and dilute
O «J
to 1 liter with water.
6.8 Sulfuric acid titrant, 0.020 N. (1.00 ml = 0.28 mg N).
6.9 Ammonium chloride, stock solution, (1.0 ml = 1.0 mg NH--N). Dissolve
3.819 g NH4C1 in water and make up to 1.0 liter with ammonia free water.
6.10 Ammonium chloride, standard solution, (1.0 ml = 0.01 mg NH_-N). Dilute
10.0 ml of the stock solution to 1.0 liter.
6.11 Nessler reagent - Dissolve 100 g of mercuric iodide and 70 g of potassium
iodide in a small volume of water. Add this mixture slowly, with
stirring, to a cooled solution of 160 g of NaOH in 500 ml of water.
Dilute the mixture to 1 liter. The solution is stable for at least one
year if stored in a pyrex bottle out of direct sunlight.
Note - Reagents 6.8, 6.9, 6.10, and 6.11 are identical to reagents 6.8, 6.2,
6.3, and 6.6 described under Nitrogen, Ammonia.
151
-------
(Nitrogen Kjeldahl, Total)
7. Procedure
7.1 The distillation apparatus should be pre-steamed before use by
distilling a 1:1 mixture of ammonia-free water and sodium hydroxide-
sodium thiosulfate solution until the distillate is ammonia free.
This operation should be repeated each time the apparatus is out of
service long enough to accumulate ammonia (usually 4 hours or more).
7.2 Place a measured sample or the residue from the distillation in the
ammonia determination (for Organic Kjeldahl only) into an 800-ml
Kjeldahl flask. The sample size can be determined from the following
table:
Kjeldahl Nitrogen
in Sample, mg/1
0 -
5 -
10 -
20 -
50 -
5
10
20
50
100
Sample Size
ml
500
250
100
50.0
25.0
Dilute the sample, if required, to 500 ml, and add 100 ml sulfuric
acid - mercuric sulfate - potassium sulfate solution (Note 2), and
evaporate the mixture in the Kjeldahl apparatus until S0» fumes are
given off and the solution turns colorless or pale yellow. Cool the
residue and add 300 ml water.
Note 2 - Alternately digest the sample with 1 Kel-Pac (Olin-Matheson)
and 20 ml cone. H-SO.. Cut the end from the package and empty the
contents into the digestion flask; discard the container.
7.3 Make the digestate alkaline by careful addition of the sodium hydroxide-
thiosulfate solution without mixing ( 20 ml of 36 N H_S04 requires
approximately 60 ml of 12.5 N NaOH-Na2S20_ to neutralize).
152
-------
(Nitrogen Kjedahl, Total)
Note - Slow addition of the heavy caustic solution down the tilted
neck of the digestion flask will cause the heavier solution to underlay
the aqueous sulfuric acid solution without loss of free ammonia. Do
not mix until the digestion flask has been connected to the distillation
apparatus.
7.4 Connect the Kjeldahl flask to the condenser with the tip of condenser
(or an extension of the condenser tip) below the level of the boric
acid solution in the receiving flask.
7.5 Distill 300 ml at the rate of 6-10 ml/min., into 50 ml of 2% boric acid
contained in a 500-ml glass stoppered Erlenmeyer flask.
i
7.5.1 If it is anticipated that the ammonia measurement will be by
nesslerization, 50 ml of boric acid is preferred. If, however,
sufficient ammonia is present to permit titration of a larger
volume of boric acid, either 100 or 200 ml, may be used.
7.6 Dilute the distillate to 500 ml in the flask and nesslerize an aliquot
to obtain an approximate value of the ammonia-nitrogen concentration.
For concentrations above 1.0 mg/1 the ammonia should be determined
titrimetrically. For concentrations below this value it is determined
colorimetrically.
7.7 Determination of ammonia in distillate - Determine the ammonia content
of the distillate either titrimetrically or colorimetrically as
described below.
7.7.1 Titrimetric determination. Add 3 drops of the mixed indicator
to the distillate and titrate the ammonia with the 0.02 N
H-SO., matching the endpoint against a blank containing the
same volume of ammonia-free water and H,BO solution.
o o
153
-------
(Nitrogen Kjeldahl, Total)
7.7.2 Colorimetric determination. Prepare a series of Nessler tube
standards as follows:
ml as Standard Cone., When Diluted to
1.0 ml = 0.01 mg NH3N 50.0 ml, mg NH3N/liter
0.0 (Blank) 0.0
0.2 0.04
0.5 0.10
1.0 0.20
1.5 0.30
2.0 0.40
3.0 0.60
4.0 0.80
Dilute each tube to 50 ml with ammonia-free water, add 1.0 ml
of Nessler reagent and mix. After 20 minutes read the optical
densities at 425 ran against the blank. From the values obtained
plot optical density (absorbance) vs. concentration for the
standard curve.
7.7.3 It is not imperative that all standards be distilled in the
same manner as the samples. It is recommended that at least 2
standards (a high and low) be distilled and compared to similar
values on the curve to insure that the distillation technique is
reliable. If distilled standards do not agree with undistilled
standards the operator should find the cause of the apparent
error before proceeding.
7.8 Determine the ammonia in the distillate by nesslerizing 50 ml or ah
aliquot diluted to 50 ml and reading the optical density at 425 nm
as described above for the Standards. Ammonia-nitrogen is read from
the standard curve.
8. Calculation
8.1 If the titrimetric procedure is used calculate Total Kjeldahl Nitrogen,
154
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(Nitrogen Kjeldahl, Total)
in mg/l, in the original sample as follows:
Total Kjeldahl nitrogen, mg/l = CA-B) x N x F x 1000
o
where:
A = milliliters of standard 0.020 N H SO. solution used in
titrating sample.
B = milliliters of standard 0.020 N H-SO. solution used in
titrating blank.
N = normality of sulfuric acid solution
F = millequivalent weight of nitrogen (14 rag).
S = milliliters of sample digested.
If the sulfuric acid is exactly 0.02 N the formula is shortened to:
TKN, mg/l = CA-B) x 280
o
8.2 If the Nessler procedure is used, calculate the Total Kjeldahl Nitrogen,
in mg/l, in the original sample as follows:
T™ m /i A x 1000
TKN, mg/l = 0-8 xg
where:
A = mg NH_N read from curve.
O
S = volume of distillate nesslerized.
8.3 Calculate Organic Kjeldahl Nitrogen in mg/l, as follows:
Organic Kjeldahl Nitrogen = TKN - NH N
• • O
9. Precision
9.1 Thirty-one analysts in twenty laboratory analyzed natural water
samples containing exact increments of organic nitrogen, with the
following results:
155
-------
(Nitrogen Kjeldahl, Total)
Increment as
Nitrogen, Kjeldahl
mg N/ liter
0.20
0.31
4.10
4.61
Precision as
Standard Deviation
mg N/liter
0.197
0.247
1.056
1.191
Accuracy
Bias,
% mg
+15.54
+ 5.45
+ 1.03
- 1.67
as
Bias,
N/liter
+ .03
+ .02
+ .04
-.08
(FWPCA Method Study 2, Nutrient Analyses)
156
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NITROGEN, KJELDAHL, TOTAL
(Automated Phenolate Method)
STORET NO. 00625
1. Scope and Application
1.1 This automated method may be used to determine Kjeldahl nitrogen
in surface waters, domestic and industrial wastes, and saline waters.
The applicable range is 0.05 to 2.0 mg N/l. Approximately 20 samples
per hour can be analyzed.
2. Summary of Method
2.1 The sample is automatically digested with a sulfuric acid solution
containing potassium sulfate and mercuric sulfate as a catalyst to
convert organic nitrogen to ammonium sulfate. The solution is then
automatically neutralized with sodium hydroxide solution and treated
with alkaline phenol reagent and sodium hypochlorite reagent. This
treatment forms a blue color designated as indophenol. Sodium nitro-
prusside, which increases the intensity of the color, is added to
obtain necessary sensitivity for measurement of low level nitrogen.
3. Definitions
3.1 Total Kjeldahl nitrogen is defined as the sum of free ammonia and of
organic compounds which are converted to (NH.)-SO. under the conditions
of digestion which are specified below.
3.2 Organic Kjeldahl nitrogen is defined as the difference obtained by
subtracting the free ammonia value from the total Kjeldahl nitrogen
value. Also, organic Kjeldahl nitrogen may be determined directly by
removal of ammonia before digestion.
4. Sample Handling and Preservation
4.1 Preservation by addition of 40 mg HgCl2 per liter and refrigeration
at 4°C is necessary.
157
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(Nitrogen, Kjeldahl, Total)
5. Interferences
5.1 Iron and chromium ions tend to catalyze while copper ions tend to
inhibit the indophenol color reaction.
6. Apparatus
6.1 Technicon AutoAnalyzer consisting of:
6.1.1 Sampler II, equipped with continuous mixer.
6.1.2 Two proportioning pumps.
6.1.3 Manifold I
6.1.4 Manifold II
6.1.5 Continuous Digester
6.1.6 Peristaltic pump
6.1.7 Five-gallon Carboy fume-trap
6.1.8 80°C Heating bath
6.1.9 Colorimeter equipped with 50 mm tubular flow cell and
630 nm filters.
6.1.10 Recorder equipped with range expander.
7. Reagents
7.1 Distilled Water: Special precaution must be taken to insure that
distilled water is free of ammonia. Such water is prepared by passage
of distilled water through an ion exchange column comprised of a
mixture of both strongly acidic cation and strongly basic anion ex-
change resins. Furthermore, since organic contamination may interfere
with this analysis, use of the resin Dowex XE-75 or equivalent which
also tends to remove organic impurities is advised. The regeneration
of the ion exchange column should be carried out according to the
instruction of the manufacturer.
158
-------
(Nitrogen, Kjeldahl, Total)
7.2 Sulfuric acid: As it readily absorbs ammonia, special precaution
must also be taken with respect to its use. Do not store bottles
reserved for this determination in areas of potential ammonia con-
tamination.
7.3 EDTA (2% solution): Dissolve 20 g disodium ethylenediamine
tetraacetate in 1 liter of distilled water. Adjust pH to
10.5-11.
7.4 Sodium hydroxide (30% solution): Dissolve 300 g NaOH in 1 liter
of distilled water.
NOTE: The 30% sodium .hydroxide should be sufficient to neutralize
the digestate.\ In rare cases it may be necessary to increase
the concentration of sodium hydroxide in this solution to insure
neutralization of the digested sample in the manifold at the
water jacketed mixing coil.
7.5 Sodium nitroprusside, Stock (1% solution): Dissolve 10 g
Na2Fe(CN)5NO-2H20 in 1 liter distilled water.
NOTE: This solution may be omitted if the nitrogen in the sample
=0.1 mg/1.
7.6 Sodium nitroprusside, working solution: Dilute 50 ml stock solution
to 1 liter with distilled water.
7.7 Alkaline phenol reagent: Pour 550 mis liquid phenol (88-90%) slowly
with mixing and cooling into 1 liter of 40% NaOH. Make up to 2
liters with distilled water.
7.8 Sodium hypochlorite (1% solution): Dilute commercial "Clorox" - 200 ml
to 1 liter with distilled water.
159
-------
(Mtrogen, Kjeldahl, Total)
7.9 Digestion mixture: Place 2 g HgO in a 2-liter container. Slowly
add, with stirring, 300 ml of acid water (100 mi H..SO. - 200 ml HO)
£ Q Z.
and stir until cool. Add 100 ml 10% K^SO.. Dilute to a volume of
2 liters with cone, sulfuric acid (approximately 500 ml at a time,
?•.
allowing time for cooling).
7.10 Stock Solution: Dissolve 4.7619 g of pre-dried ammonium sulfate
(1 hour at 105°C) in distilled water and dilute to 1.0 liter.
Dissolve 2.1276 g of urea (desiccate only) in distilled water and dilute
to 1.0 liter. Dissolve 10.5263 g of glutamic acid (desiccate only)
in distilled water and dilute to 1.0 liter. 1 ml = 1.0 mg N.
7.11 Standard Solution: Dilute 10.0 ml of respective stock solutions to
1.0 liter. 1 ml = 0.01 mg N.
7.10.1 Using the respective standard solutions, prepare the
following standards in 100.0 ml volumetric flasks:
Cone., mg N/l ml Standard Solution/100 ml
0.00 0.0
0.05 0.5
0.10 1.0
0.20 2.0
0.40 4.0
0.60 6.0
0.80 8.0
1.00 10.0
1.50 15.0
2.00 20.0
8. Procedure
8.1 Set up manifolds as shown in Figures 1, 2, and 3.
8.1.1 In the operation of Manifold No. 1, the control of three
key factors is required to enable Manifold No. 2 to
receive the mandatory representative feed. First, the digestate
160
-------
(Nitrogen, Kjeldahl, Total)
flowing into the pulse chamber (PC-1) must be bubble free,
otherwise, air will accumulate in A-7, thus altering the
ratio of sample to digestate in digestor. Second, in main-
taining even flow from the helix, the peristaltic pump must
be adjusted to cope with differences in density of the
digestate and the wash water. Third, the sample pick-up rate
from the helix must be precisely adjusted to insure that the
entire sample is aspirated into the mixing chamber. And
finally, the contents of the "Mixing Chamber" must be kept
homogeneous by the proper adjustment of the air bubbling
rate.
8.1.2 In the operation of Manifold No. 2, it is important in the
neutralization of the digested sample to adjust the concen-
tration of the NaOH so that the waste from the C-3 debubbler
is slightly acid to Hydrion B paper.
8.1.3 The digester temperature is 390°C for the first stage and
360°C for the second and third stages.
8.2 Allow both colorimeter and recorder to warm up for 30 minutes. Run
a baseline with all reagents, feeding distilled water through the
sample line. Adjust dark current and operative opening on colorimeter
to obtain stable baseline.
8.3 Set sampling rate of Sampler II at 20 samples per hour, using a wash
to sample ratio of 2 to 1 (1 minute sample, 2 minute wash).
NOTE: With a 2 minute sampling time plus two 2 minute washes, this
actually represents 10 samples/hr.
161
-------
(Nitrogen, Kjeldahl, Total)
8.4 Arrange various standards in Sampler cups in order of increasing
concentration. Complete loading of sampler tray with unknown
samples.
8.5 Switch sample line from distilled water to sampler and begin analysis.
8.5.1 If equipment is operating properly, 100% nitrogen recovery
should be obtained for glutamic acid and urea when compared
to ammonium sulfate standards.
9. Calculation
9.1 Prepare standard curve by plotting peak heights of processed standards
against concentration values. Compute concentration of samples by
comparing sample peak heights with standard curve.
9.2 Any sample that has a computed concentration that is less than 10%
of the sample run immediately prior to it must be rerun.
10. Precision and Accuracy
10.1 Six laboratories analyzed four natural water samples containing exact
increments of organic nitrogen compounds, with the following results:
Increment as
Kjeldahl-Nitrogen
mg N/ liter
1.89
2.18
5.09
5.81
Precision as
Standard Deviation
Kjeldahl-N, mg N/liter
0.54
0.61
1.25
1.85
Bias
%
-24.6
-28.3
-23.8
-21.9
Accuracy as
, Bias,
mg N/liter
- .46
- .62
-1.21
-1.27
(FWQA Method Study 4, Automated Methods - In preparation).
162
-------
(Nitrogen, Kjeldahl, Total)
References
1. Kammerer, P. A.; Rodel, M. G.; Hughes, R. A.; and Lee, G. F.; "Low Level
Kjeldahl Nitrogen Determination on the Technicon AutoAnalyzer." Environ-
mental Science and Technology. 1:4:340 (April 1967).
2. McDaniel, William H.; Hemphill, R. N.; Donaldson, W. T.; "Automatic
Determination of Total Kjeldahl Nitrogen in Estuarine Waters." Presented
at Technicon Symposium on Automation in Analytical Chemistry, New York,
October 3, 1967.
3. B. O'Connor, Dobbs, Villiers, and Dean, "Laboratory Distillation of
Municipal Waste Effluents". JWPCP 39_, R 25, 1967.
163
-------
WASH WATER (TO SAMPLER 2
Ml)
COOLING WATER;* (
CUUM PUMP §
i
* * r^^f^V^XTru
- \liS\\\\\l r"™^
\l 1 \ V \ \ \ \1 1
INATARY
DIIUD
SMALL
(ING COIL
*
4
*
0 <"
0 i
LARGE MIXING
COIL
- J
DIGESTOR
G G
BLUE BLUE
G G
BLUE BLUE
P B
P B
P W
P W
ml/min.
^2.00 WASH WATER
(1.60 SAMPLE
t2.00 DISTILLED WATER /6°®C
J.60 AIR* (o O
- \&
.2.03 DIGESTAHT -<
,1.11 OI6ESTAMT "»'"
t3.90 DISTILLED WATER
.3.90 DISTILLED WATER
'•"X * » *
) FOI
> WA
FOR SALT
WATER
SAMPLES
MIXING CHAMBER
AIR
PROPORTIONING PUMP
*AIR IS SCRUBBED THRU 5N H2S04
"TEFLON TUBING OR GLASS
***FOR FRESH WATER SAMPLES USE:
r B
P
G
Y
P
G.
Y
z .bu n«ii
2.50 SAMP
2.00 DISTI
1.20 AIR*
WATER
FIGURE 1. KJELDAHL NITROGEN - MANIFOLD 1
-------
CONTINUOUS DIGESTER & MIXING CHAMBER ASSEMBLY
TO ASPIRATOR
0\
ON
DILUTION WATER
5 GALLON
FUME CARBON TRAP
HALF FILLED WITH
40% NaOH
CONNECTED TO
ASPIRATOR
TO SUMP U
TO ASPIRATOR
LINE DESIGNATION:
1. OXIDIZED SAMPLE
2. AIR AGITATION
3. MIXING CHAMBER OVERFLOW
4. WASTE
5. FEED TO MANIFOLD NO. 2
TO MANIFOLD NO. 2
FIGURE 2. KJELDAHL NITROGEN
-------
C-3
CO
V
i
LM
i
J
LARGE MIXII
OOOOOOOO
I
••
^m
ACKETED R
46 COILS
OOOi
k
L
A A
*J \
AIXLH 1
(LM)
OMOO
*
f
SMALL MIXING COIL
N\ 2x40 '
l°yj) COIL LM
^ , oooooooo
WASTE.
i
COLORIMETER
50mm TUBULAR f/c
630 nm FILTERS
PROP
BLUE BLUE
G G
R R
Y Y
P 1
Y Y
R R
If It
Y Y
Y Y
Y Y
P 0
OPTIONING PI
1 1 _
51 r"
Tl f
ml/min.
.1.60 SAMPLE FROM MIXING CHAMBER
^.OO NaOH (SEE MANIFOLD 1 J
,0.80 DISTILLED WATER
1.20 AIR
72.90 SAMPLE 4
,1.20 EDTA
40.80 AIR
,0.80 DISTILLED WATER
,1.20 ALK. PHENOL
,1.20 NaOCL
(1.20 NITROPRUSSIOE
.3.40 WASTE
IMP
-
RECORDER
^ ^"
FIGURE 3. KJELDAHL NITROGEN MANIFOLD 2.
-------
1. Scope and Application
NITROGEN, NITRATE
STORET NO. 00620
1.1 This method is applicable to the analysis of surface waters, domestic
and industrial wastes, and saline waters. Modification can be made to
remove or correct for turbidity, color, salinity, or dissolved organic
compounds in the sample.
1.2 The applicable range of concentrations is 0.1 to 2 mg NO,N/liter.
2. Summary of Method
2.1 This method is based upon the reaction of the nitrate ion with brucine
sulfate in a 13 N H2S04 solution at a temperature of 100°C. The color of
the resulting complex is measured at 410 nut- Temperature control of the
color reaction is extremely critical.
i
i
3. Sample Handling and Preservation
3.1 Until more conclusive data is obtained, samples may be preserved by
addition of 40 mg HgCl- per liter and storage at 4°C.
4. Interferences
4.1 Dissolved organic matter will cause an off color in 13 N H?SO. and must
be compensated for by additions of all reagents except the brucine-sul-
fanilic acid reagent. This also applies to natural color present not
due to dissolved organics.
4.2 The effect of salinity is eliminated by addition of sodium chloride to
the blanks, standards and samples.
4.3 All strong oxidizing or reducing agents interfere. The presence of
oxidizing agents may be determined by the addition of orthotolidine
reagent.
4.4 Residual chlorine interference is eliminated by the addition of sodium
arsenite.
170
-------
(Nitrogen, Nitrate)
4.5 Ferrous and ferric iron and quadrivalent manganese give slight
positive interference, but in concentrations less than 1 mg/1 these
are negligible.
4.6 Uneven heating of the samples and standards during the reaction time
will result in erratic values. The necessity for absolute control of
temperature during the critical color development period cannot be too
strongly emphasized.
5. Apparatus
5.1 Spectrophotometer or filter photometer suitable for measuring optical
densities at 410 nm and capable of accommodating 25 mm diameter cells.
5.2 Sufficient number of 25 mm diameter matched tubes for reagent blanks,
standards, and samples.
5.3 Neoprene coated wire racks to hold 25 mm diameter tubes.
5.4 Water bath suitable for use at 100°C. This bath should contain a
stirring mechanism so that all tubes are at same temperature and should
be of sufficient capacity to accept the required number of tubes without
significant drop in temperature when the tubes are immersed.
5.5 Water bath suitable for use at 10-15°C.
6. Reagents
6.1 Distilled water free of nitrite and nitrate is to be used in preparation
of all reagents and standards.
6.2 Sodium chloride solution (300 g/1). Dissolve 300 g NaCl in distilled
water and dilute to .1.0 1.
6.3 Sulfuric acid solution. Carefully add 500 ml H2S04 (sp. gr. 1.84) to
125 ml distilled water. Cool and keep tightly stoppered to prevent
absorption of atmospheric moisture.
171
-------
(Nitrogen, Nitrate)
6.4 Brucine-sulfanilic acid reagent. Dissolve 1 g brucine sulfate
[CC23H26N204)2.H2S04.7H20] and 0.1 g sulfanilic acid
in 70 ml hot distilled water. Add 3 ml concentrated HC1, cool, mix and
dilute to 100 ml. Store in a dark bottle at 5°C. This solution is stable
for several months; the pink color that develops slowly does not effect
its usefulness. Mark bottle with warning: CAUTION: Brucine Sulfate is
toxic; take care to avoid ingest ion.
6.5 Potassium nitrate stock solution (1 ml = 0.1 mg NCL-N) . Dissolve 0.7218 g
anhydrous potassium nitrate (KNO_) in distilled water and dilute to 1
O
liter.
6.6 Potassium nitrate standard solution Q ml = Q.QQ1 me NO -N) . Dilute 10.0 ml
\ o
of the stock solution to 1 liter. This standard solution should be
prepared fresh weekly.
6.7 Acetic acid (1 +3). Dilute 1 vol. glacial acetic acid (CH-COOH) with
3 volumes of distilled water.
7. Procedure
7.1 Adjust the pH of the samples to approximately pH 7 with 1:3 acetic acid
and, if necessary, filter through a 0.45p pore size filter.
7.2 Set up the required number of matched tubes in the rack to handle
reagent blank, standards and samples. It is suggested that tubes be
spaced evenly throughout the rack to allow for even flow of bath water
between the tubes. Even spacing of tubes should assist in achieving
uniform heating of all tubes.
7.3 If it is necessary to correct for color or dissolved organic matter which
will cause color on heating, a set of duplicate tubes must be used to
which all reagents except the brucine-sulfanilic acid has been added.
172
-------
(Nitrogen, Nitrate)
7.4 Pipette 10.0 ml or an aliquot of the samples diluted to 10.0 ml
into the sample tubes.
7.5 If the samples are saline, add 2 ml of the 30 percent sodium
chloride solution to the reagent blank, standards and samples. For
fresh water samples, sodium chloride solution may be omitted. Mix
contents of tubes by swirling and place rack in cold water bath
(0-10°C).
7.6 Pipette 10.0 ml of sulfuric acid solution into each tube and mix
by swirling. Allow tubes to come to thermal equilibrium in the
cold bath. Be sure that temperatures have equilibrated in all
tubes before continuing.
7.7 Add 0.5 ml brucine-sulfanilic acid reagent to each tube (except the
interference control tubes) and carefully mix by swirling, then place
the rack of tubes in the boiling water bath for exactly 25 minutes.
CAUTION: Immersion of the tube rack into the bath should not decrease
the temperature of the bath more than 1 to 2°C. Flow of bath water
between the tubes should not be restricted by crowding too many tubes
into the rack, in order to keep this temperature decrease to an
absolute minimum. If color development in the standards reveals
discrepancies in the procedure the operator should repeat the procedure
after reviewing the temperature control steps.
7.8 Remove rack of tubes from the hot water bath and immerse in the cold
water bath and allow to reach thermal equilibrium (20-25°C).
7.9 Dry tubes and read optical density against the reagent blank at 410 nm.
8. Calculation
8.1 Obtain a standard curve by plotting the optical densities of standards
run by the above procedure against mg NO,-N. (The color reaction does
173
-------
9.
(Nitrogen, Nitrate)
not always follow Beer's law).
8.2 Subtract the absorbance of the sample without the brucine-sulfanilic
reagent from the absorbance of the sample containing brucine-sul-
fanilic acid and read the optical density in mg NO_-N. Multiply by
factor for converting mg per aliquot of sample to mg per liter.
Precision and Accuracy
9.1 Twenty-seven analysts in fifteen laboratories analyzed natural water
samples containing exact increments of inorganic nitrate, with the
following results:
Increment as 1
Nitrogen, Nitrate |
mg N/liter
0.16
0.19
1.08
1.24
Precision as
Standard Deviation
mg N/liter
.092
.083
.245
.214
Accuracy as
Bias, Bias,
% mg N/liter
-6.79 -.01
+8.30 +.02
+4.12 +.04
+2.82 +.04
(FWPCA Method Study 2, Nutrient Analyses).
174
-------
NITROGEN, NITRATE-NITRITE
(Automated Cadmium Reduction Method)
, , .. . STORET NO. 00630
1. Scope and Application >—
1.1 This method pertains to the determination of nitrates and nitrites,
singly or combined, present in surface and saline waters. The pre-
scribed specifications permit analyses of samples in the range of
0.05 to 10 mg/liter, N present as N0_. -
2. Summary of Method' '
(2)
2.1 The initial step J is to reduce the nitrates to nitrites by using
a cadmium-copper catalyst. The nitrites (those originally present
plus reduced nitrates) are then reacted with sulfanilamide to form
the diazo compound which is then coupled in an acid solution (pH 2.0 -
2.5) with N-l naphthyl-ethylenediamine hydrochloride to form the azo
dye. The azo dye intensity, which is proportional to the nitrate con-
centration, is then measured. Separate rather than combined nitrate-
nitrite values are readily obtainable by carrying out the procedure—
first with, and then without, the initial Cd-Cu reduction step.
3. Sample Handling and Preservation
3.1 Preservation by addition of 40 mg HgCl2 per liter and refrigeration
at 4°C is necessary.
4. Interferences
4.1 Ammonia and primary amines which are frequently present in natural
waters may react to some extent with nitrites to form nitrogen. Thus,
since, as in nature, the sample is not stable, the analyses should be
performed as soon as possible.
175
-------
(Nitrogen, Nitrate-Nitrite)
4.2 In surface waters normally encountered in surveillance studies, the
concentration of oxidizing or reducing agents and potentially inter-
fering metal ions are well below the limits causing interferences.
When present in sufficient concentration, metal ions may produce a
positive error, i.e., Hg (II) and Cu (II), may form colored complex
ions having absorption bands in the region of color measurement.
5. Apparatus
5.1 Technicon AutoAnalyzer consisting of the following components:
5.1.1 Sampler II.
5.1.2 Manifold (including Cu-Cd column).
5.1.3 Colorimeter equipped with 50 mm tubular flow cell and
|
540 nm filters.
i
5.1.4 Range expander.
5.1.5 Recorder.
(2)
5.2 Cadmium-copper reduction column .
5.2.1 Preparation: Shake the 30 - 60 mesh av. diam. 0.5 mm cadmium
turnings with a solution of 2% (wt/vol) copper sulfate
pentahydrate solution. A weight of solution equal to 10 times
the weight of the cadmium is used. The copper sulfate-treated
cadmium catalyst is then placed in a 8 mm x 50 mm pyrex tubing
and is followed by copper granules (0.6 mm x 3.0 mm) made from
hydrogen treated copper wire (Note 1). The volume ratio of the
cadmium bed to that of the copper should be about 3 - 1 to
4-1. (See Figure 1). Pyrex wool, inserted at the lower end
of the reactor, is used to prevent the catalyst from dropping
out of the reactor. The ends of the reactor are fabricated to
176
-------
(Nitrogen, Nitrate-Nitrite)
accomodate the reactor into the system. :The sample enters
the column at the copper granule-packed end. To minimize
back pressure due to a vertical position or channelling due
to a horizontal position, the reductant tube is placed in an
up-flow 20° incline.
Note 1 - Supplied by F§M Scientific Corp,, Avondale, Pa.
5.2.2 Regeneration: HC1, diluted 1 to 4, is pumped through the
NH.C1 line for one minute, followed by water for two minutes
and then 2% copper sulfate solution for five minutes. For
complete cleaning and coating, remove the.column from the
manifold. Using a small funnel and a short plastic connecting
tube, the acid water and copper sulfate solution are successively
poured into the column and allowed to flow through by gravity.
The cadmium should ultimately acquire a moss-black appearance
and the copper, a bright orange.
6. Reagents
6.1 Distilled water: Because of possible contamination, this should be
prepared by passage through an ion exchange column comprised of
a mixture of both strongly acidic-cation and strongly basic-anion
exchange resins. The regeneration of the ion exchange column should
be carried out according to the manufacturer's instructions.
6.2 Color reagent: To approximately 800 ml of distilled water, add, while
stirring, 100 ml concentrated phosphoric acid, 40 g sulfanilamide, and
2 g N-l naphthylethylenediamine dihydrochloride. Stir until dissolved
and dilute to one liter. Store in brown bottle and keep in the dark
when not in use. This solution is stable for several months.
177
-------
• (Nitrogen, Nitrate-Nitrite)
6.3 Wash solution: Use distilled water for unpreserved samples; samples
preserved with H2S04, use 1 ml H2S04 per liter of wash water.
6.4 Ammonium Chloride Solution (8.5% NH.C1): Dissolve 85 g of reagent
grade ammonium chloride in distilled water and dilute to one liter
with distilled water. Add 1/2 ml Brij-35^4).
6.5 Stock nitrate solution: Dissolve 7.218 g KNO_ and dilute to 1.0 1
with distilled water. Preserve with 2 ml of chloroform per liter.
Solution is stable for 6 months. 1 ml = 1.0 mg NO_-N.
6.6 Stock nitrite solution: Dissolve 6.072 g KNO_ and dilute to 1.0 1
with distilled water. Solution is unstable; prepare as reauired.
1 ml = 1.0 mg NO -N.
|
6.7 Standard nitrate solution: Dilute 10.0 ml of stock nitrate solution
to 1 liter. 1 ml = 0.01 mg NO--N. Preserve with 2 ml of chloroform
O
per liter. Solution is stable for 6 months.
6.8 Standard nitrite solution: Dilute 10.0 ml of stock nitrite solution
to 1 liter. 1 ml = 0.01 mg NO^-N. Solution is unstable; prepare as
required.
6.9 Using either standard nitrate solution or standard nitrite solution,
prepare the following standards in 100.0 ml volumetric flasks:
Cone., mg N03-N or N02-N/1 Standard Solution/100 ml
0.0 0
0.05 0.5
0.10 1.0
0.20 2.0
0.50 5.0
1.00 10.0
2.00 20.0
4.00 40.0
6.00 60.0
Note: When the samples to be analyzed are saline waters, substitute
Ocean Water (SOW) (5) should be used for preparing the standards;
178
-------
INDENTATIONS FOR
SUPPORTING CATALYST
GLASS WOOL
Cd-TURNINGS
Cu-FILINGS (FINE MESH)
TILT COLUMN TO 20° POSTION
FIGURE 1. CADMIUM-COPPER REDUCTION COLUMN
(1 1/2 ACTUAL SIZE)
179
-------
(Nitrogen, Nitrate-Nitrite)
otherwise, distilled water is used. A tabulation of SOW
composition follows:
NaCl - 24.53 g/1 MgCl2 - 5.20 g/1 Na2S04 - 4.09 g/1
CaCl2 - 1.16 g/1 KC1 - 0.70 g/1 NaHC03 - 0.20 g/1
KBr - 0,10 g/1 H3B03 - 0.03 g/1 SrCl2 - 0.03 g/1
NaF - 0.003 g/1
7. Procedure
7.1 Set up the manifold as shown in Figure 2. Note that reductant column
should be in 20° incline position with Cu at lower end.
7.2 Allow both colorimeter and recorder to warm up for 30 minutes. Run
a baseline with all reagents, feeding distilled water through the
i
sample line. Adjust dark current and operative opening on colorimeter
to obtain stable baseline.
7.3 Place appropriate nitrate and/or nitrite standards in sampler in order
of decreasing concentration of nitrogen. Complete loading of sampler
tray with unknown samples.
7.4 Switch sample line to sampler and start analysis.
8. Calculations
8.1 Prepare appropriate standard curve or curves derived from processing
N0_ and/or N0_ standard through manifold. Compute concentration of
O £•
samples by comparing sample peak heights with standard curve. Any
sample whose computed concentration is less than 10% of its immediate
predecessor must be rerun.
9. Precision and Accuracy
9.1 Three laboratories analyzed four natural water samples containing
exact increments of inorganic nitrate, with the following results:
181
-------
(Nitrogen, Nitrate-Nitrite)
Increment as
Nitrate Nitrogen
mg N/Liter
0.29
0.35
2.31
2.48
Precision as
Standard Deviation
mg N/ liter
0.012
0.092
0.318
0.176
Accuracy
Bias,
%
+ 5.75
+18.10
+ 4.47
- 2.69
as
Bias,
mg N/ liter
+ .017
+ .063
+ .103
-.067
(FWQA Method Study 4, Automated Methods - In preparation)
References
1. J. E. O'Brien and J. Fiore, "Automation in Sanitary Chemistry - parts
1 £ 2 Determination of Nitrates and Nitrites." Wastes Engineering, 33,
128 5 238 (1962).
2. J. D. Strickland, C. R. Stearns, and F. A. Armstrong, "The Measurement
of Upwelling and Subsequent Biological Processes by Means of the Technicon
AutoAnalyzer and Associated Equipment." Deep Sea Research 14, 381-389
(1967).
3. "ASTM Manual on Industrial Water and Industrial Waste Water," Method D
1254, page 465 (1966).
4. Chemical Analyses for Water Quality Manual, Department of the Interior,
FWPCA, R. A. Taft Sanitary Engineering Center Training Program, Cincinnati,
Ohio 45226 (January 1966).
5. "ASTM Manual on Industrial Water and Industrial Waste Water," Substitute
Ocean Water, Table 1, page 418, 1966 edition.
182
-------
WASTE
oo
OJ
00000000
DOUBLE MIXER
WASTE
TO SAMPLE WASH
ml/min
PS-3
oooo
HO
C-3* MIXER
WASTE
[DO
COLUMN **
BLUE
0
BLUE
BLUE
BLUE
0.42
1.60
HoO
0.80 AIR
2.00
H90
0.42 COLOR REAGENT
2.00
1.60 SAMPLE
1.20 8.5% NHACL.
1.20 AIR
COLORIMETER
50mm TUBULAR f/c
540rrm FILTERS
PROPORTIONING PUMP
RECORDER
SAMPLER 2
RATE: 30 PER HR.
* FROM C-3 TO SAMPLE LINE USE
.030 x .048 POLYETHYLENE TUBING.
** SEE FIGURE 1. FOR DETAIL. COLUMN
SHOULD BE IN 20° INCLINE POSITION
RANGE EXPANDER
WITH Cu AT LOWER END.
FIGURE 2. NITRATE-NITRITE MANIFOLD
-------
NITROGEN, NITRATE AND NITRITE
(Automated Hydrazine Reduction Method)
STORET NO. 00630
1. Scope and Application
1.1 This method is applicable to surface waters, and domestic and
industrial wastes which contain less than 500 mg/1 calcium. The
applicable range of this method is 0.05-10 mg/1 nitrite or nitrate
nitrogen. Approximately 20 samples per hour can be analyzed.
2. Summary of Method
2.1 This method, using the Technicon AutoAnalyzer, determines NO.-N
by the conventional diazotization-coupling reaction. The NO--N is
reduced with hydrazine sulfate in another portion of the sample and
the nitrite thus formed is determined in the usual manner.
|
2.2 Subtraction of the NCL-N originally present in the sample from the
total NO--N found will give the original NO--N concentration in terms
of N02-N.
3. Sample Handling and Preservation
3.1 Preservation by addition of 40 mg HgCl- per liter and refrigeration
at 4°C.
4. Interferences
4.1 The following table lists the concentration of ions that cause no
interference in the determination of nitrite and nitrate nitrogen.
The same interfering ion concentration applies to either nitrite or
nitrate:
185
-------
(Nitrogen, Nitrate and Nitrite)
Ion mg/1 Ion Not Causing Interference
Cl~ 30,000
P04"3 50
S"2 Note
NH3-N 80
Mg+2 75
Ca+2 240
Fe+3 30
ABS 60
Note 1. — The apparent NCL and NCL concentrations varied
* 10 percent with concentrations of sulfide ion up to 10 mg/1.
4.2 The pH of the samples should be between 6 and 9.
5. Apparatus
5.1 Technicon AutoAnalyzer consisting of:
5.1.1 Two proportional pumps.
5.1.2 Two colorimeters each with an 8 mm flow-through cell and
520 nm filters.
5.1.3 One continuous filter.
5.1.4 One Sampler I.
5.1.5 Two recorders.
5.1.6 One 38°C temperature bath.
5.1.7 Two time delay coils.
6. Reagents
6.1 Color developing reagent: To approximately 3 liters of distilled
water add 400 ml concentrated phosphoric acid (sp. gr. 1.834), 60 g
186
-------
(Nitrogen, Nitrate and Nitrite)
sulfanilamide (H2H-C6H4S02NH2) followed by 3.0 g N (1-Naphthyl)
ethylene-diamine dihydrochloride. Dilute the solution to 4 liters
with distilled water and store in a dark bottle in the refrigerator.
This solution is stable for approximately 1 month.
NOTE 2: It may be necessary to apply heat in order to dissolve
the sulfanilamide.
6.2 Copper sulfate; stock solution: Dissolve 2.5 g of copper sulfate
(CuS0..5H20) in distilled water and dilute to 1 liter.
6.3 Copper sulfate; dilute solution: Dilute 20 ml of stock solution to
2 liters with distilled water.
6.4 Sodium hydroxide; stock solution, CIO N): Dissolve 400 g NaOH in
750 ml distilled water, cool and dilute to 1 liter.
i
I
6.5 Sodium hydroxide (l.ON): Dilute 100 ml of stock NaOH solution to
1 liter.
6.6 Sodium hydroxide (0.3N): Dilute 60 ml of stock NaOH to 2 liters.
6.7 Hydrazine sulfate; stock solution: Dissolve 54.92 g of hydrazine
sulfate (N2H .H2SOJ in 1800 ml of distilled water and dilute to
2.0 1. This solution is stable for approximately 6 months.
CAUTION: Toxic if ingested. Mark container with warning.
6.8 Hydrazine sulfate; dilute solution: Dilute 90 ml of stock solution
to 4 liters with distilled water to obtain working solution. Make
up fresh daily.
6.9 Potassium nitiate; stock solution (1000 mg/1 . NO -N): Dissolve
7.2180 g of KNO,, oven dried at 100-105°C for 2 hours, in distilled
«J
water and dilute to 1.0 1. Add 1 ml chloroform as a preservative.
Stable for 6 months.
187
-------
(Nitrogen, Nitrate and Nitrite)
6.10 Potassium nitrate; standard solution (100 mg/1 NO--N): Dilute
50 ml of stock KNO_ solution to 500 ml in a volumetric flask.
From this dilute'solution prepare the following standards in 500 ml
volumetric flasks:
mg/1 NO--N ml Standard Solution
0.4 2.0
1.0 5.0
1.6 8.0
3.0 15.0
5.0 25.0
7.0 35.0
10.0 50.0
6.11 Sodium nitrite; stock solution (1000 mg/1 N02-N) : Dissolve 4.9260 g
NaNCL, oven dried at 100-105°C for two hours, in distilled water
and dilute to 1-0 1- Add 1 ml chloroform as preservative. Store
in the refrigerator. Stable for 1 month.
6.12 Sodium nitrite; standard solution (100 mg/1): Dilute 50 ml of stock
NaNO~ solution to 500 ml in a volumetric flask. From this dilute
solution prepare the same volumetric standards as in 6.9. Prepare
fresh each week.
7. Procedure
7.1 Set up the manifold as shown in Figures 1 and 2. Allow both color-
imeter (with the proper filters) and recorder to warm up for 30
minutes, then run a baseline with all reagents, feeding distilled
water through the sample line. Adjust dark current and operative
opening on each colorimeter. Adjust baseline to 0.01 optical density.
Place a distilled water wash tube in alternate openings on sampler
and set sample timing at 1.5 minutes.
188
-------
--'" ' .r--;.;•! (Nitrogen, Nitrate and Nitrite)
7.2 Run a 2.0 mg/1 NO -N and a 2.0 mg/1 N00-N standard through the
•J £,
system to check for 100% reduction of nitrate to nitrite. The two
peaks should be of equal height. If the NO peak is lower than that
of the N02 peak, the temperature of the reduction bath should be
increased until they are equal. If the NO peak is higher than the
•J
nitrate, the temperature should be reduced. When the correct tem-
perature of the bath has been determined, no further adjustment should
be necessary.
7.3 Arrange standards in sampler in N0,-N0_ order with increasing con-
£. «J
centration of nitrogen. Place unknown samples in sampler tubes and
place in alternate openings of sampler. A N0_ and NO, standard of
. - . - | - .. 23.
equal nitrogen concentration should be placed after every 10 samples
1 -
as a further check on the system and to more easily identify peaks.
8. Calculation
8.1 Prepare standard curve by plotting peak heights of processed standards
against known concentrations. Compute concentrations of samples by
comparing sample peak heights with standard curve.
8.2 Subtract the N0» concentration in the sample from the total N0_
found (nitrite plus nitrate) on the reduction side to calculate the
NO, concentration in the sample.
O - ' • '
9. Precision and Accuracy
9.1 Nine laboratories analyzed four natural water samples containing
exact increments of inorganic nitrate, with the following results:
189
-------
(Nitrogen, Nitrate and Nitrite)
Increment as
Nitrate Nitrogen
mg N/ liter
0.29
0.35
2.31
2.48
Precision as
Standard Deviation
mg N/liter
0.053
0.058
0.258
0.217
Bias,
%
-0.8
+ 1.9
+ 3.0
-1.2
Accuracy as
Bias,
mg N/liter
.002
.007
.07
.03
CFWQA Method Study 4, Automated Method - In preparation).
9.2 In a single laboratory CAQC), using surface water samples at concen-
trations of 0.1, 0.2, 0.8, and 2.1 mg-N/1, the standard deviations
were 0.0, ±0.04, ±0.05, and ±0.05, respectively.
9.3 In a single laboratory (AQC), using surface water samples at concen-
trations of 0.2 and 2.2 mg N/l, recoveries were 100% and 96%, respec-
tively.
References
1. D. Jenkins and L. Medsker, "Brucine Method for Determination of Nitrate
in Ocean, Estuarine, and Fresh Waters." Anal. Chem., 56, 610 (1964).
2. L. Kamphake, S. Hannah, and J. Cohen, "Automated Analysis for Nitrate
by Hydrazine Reduction." Water Research, 1_, 205 (1967).
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NITROGEN, NITRITE
STORET NO. 00615
1. Scope and Application
1.1 This method is applicable to the determination of nitrite in surface
waters, domestic and industrial wastes and saline waters.
1.2 The method is applicable in the range from 0.05 to 1.0 mg/1 NO-/N.
2. Summary of Method
2.1 The diazonium compound formed by diazotation of sulfanilamide by
nitrite in water under acid conditions is coupled with N-(l-naphthyl)-
ethylenediamine to produce a reddish-purple color which is read in a
spectrophotometer at 540 nm.
3. Sample Handling and Preservation
3.1 Until more conclusive data are obtained, samples may be preserved bv
addition of 40 mg HgCl™ per liter and stored at 4°C.
4. Interferences
4.1 There are very few known interferences at concentrations less than 1,000
times that of the nitrite; however, recent addition of strong oxidants
or reductants to the samples will readily affect the nitrite concen-
trations. High alkalinity (>600 mg/1) will give low results due to a
shift in pH of the color reaction.
5. Apparatus
5.1 Spectrophotometer equipped with 1.0 and 5.0 cm cuvettes for use at
540 nm.
5.2 Nessler tubes, 50 ml or volumetric flasks, 50 ml.
6. Reagents
6.1 Distilled water free of nitrite and nitrate is to be used in preparation
of all reagents and standards.
195
-------
• (Nitrogen, Nitrite)
6.2 Buffer-color reagent. To 250 ml of distilled water, add 105 ml
concentrated hydrochloric acid, 5.0 g sulfanilamide and 0.5 g N-
(1-Naphthyl) ethylenediamine dihydrochloride. Stir until dissolved.
Add 136 g of sodium acetate and again stir until dissolved. Dilute
to 500 ml with distilled water. This solution is stable for several
weeks if stored in the dark.
6.3 Nitrite-nitrogen stock solution, 1.0 ml = 0.10 mg NCL-N. Dissolve
0.4926 g of dried anhydrous sodium nitrite (24 hours in desiccator)
in distilled water and dilute to 1.0 1. Preserve with 2 ml chloroform
per liter.
6.4 Nitrite-nitrogen standard solution, 1.0 ml = 0.001 mg NO--N. Dilute
10 ml of the stock solution to 1.0 liter.
7. Procedure
7.1 If the sample has a pH greater than 10 or a total alkalinity in excess
of 600 mg/1, adjust to approximately pH 6 with 1:3 HC1.
7.2 Filter the sample through a 0.45 y pore size filter using the first
portion of filtrate to rinse the filter flask.
7.3 Place 50 ml of sample, or an aliquot diluted to 50 ml, in a 50 ml
Nessler tube; hold until preparation of standards is completed.
7.4 At the same time prepare a series of standards in 50 ml Nessler tubes
as follows:
ml of Standard Solution Cone., When Diluted to
1.0 ml = 0.001 mg NC>2-N 50 ml, mg/1 of N02-N
0.0 (Blank) 0.0
0.5 0.01
1.0 0.02
1.5 0.03
2.0 0.04
3.0 0.06
4.0 0.08
5.0 0.10
10.0 0.20
196
-------
(Nitrogen, Nitrite)
7.5 Add 2.0 ml of buffer-colored reagent to each standard and sample,
mix and allow color to develop for at least 15 minutes. The color
reaction medium should be between pH 1.5 and 2.0.
7.6 Read the color in the spectrophotometer at 540 nm against the blank
and plot concentration of NO--N against optical density.
8. Calculation
8.1 Read the concentration of N02-N directly from the curve.
8.2 Calculate the concentration of NO_-N in the sample in milligrams per
liter as follows:
wn N /i absorbance of sample x mg/1 standard x 50
U2 ' mg/ ~ absorbance of standard x ml sample
9. Precision and Accuracy
9.1 Precision and accuracy data are not available at this time.
197
-------
NITROGEN, ORGANIC + AMMONIA
(Automated Phenolate Method)
STORE! NO. 00635
1. Scope and Application
1.1 This automated method is applicable to surface and saline waters.
The applicable range is 1.0 to 10.0 mg N/l. Approximately 15 samples
per hour can be analyzed.
2. Summary of Method
2.1 Organic nitrogen is determined by manually digesting the sample with
potassium persulfate and sulfuric acid to convert the organic nitrogen,
and any ammonia present, to ammonium sulfate. Subsequently, the
automated phenol-hypochlorite procedure is used to measure the ammonia
nitrogen. Nitrate-nitrite nitrogen is not measured by this procedure.
3. Sample Handling and Preservation
3.1 Preservation by addition of 40 mg HgCl2 per liter and refrigeration
at 4°C is necessary.
4. Interferences
4.1 No significant interferences.
5. Apparatus
5.1 Technicon AutoAnalyzer consisting of:
5.1.1 Sampler I.
5.1.2 Continuous Filter.
5.1.3 Manifold.
5.1.4 Proportioning Pump.
5.1.5 Colorimeter equipped with 15 mm tubular flow cell and 650 nm
filters.
5.1.6 Recorder equipped with range expander.
5.2 Hot plate.
198
-------
(Nitrogen, Organic
+ Ammonia)
6. Reagents
6.1 Distilled Water: Special precaution must be taken to insure that
distilled water is free of ammonia. Such water is prepared by
passage of distilled water through an ion exchange column comprised
of a mixture of both strongly acidic cation and strongly basic anion
exchange resins. Since organic contaminants may interfere with this
analysis, use of the resin Dowex XE-75 or equivalent which also tends
to remove organic impurities is advised. The regeneration of the ion
exchange column should be carried out according to the instructions of
the manufacturer.
Note: All glassware must be pre-rinsed with this ammonia-free water
to prevent contamination.
\
6.2 Sulfuric Acid: As it readily absorbs ammonia, special precaution must
also be taken with respect to its use. Do not store bottles reserved
for this determination in areas of potential ammonia contamination.
6.3 Potassium persulfate, low N (0.001%): Certain lots of this reagent do
not meet this specification for nitrogen content. In order to insure
this purity, dissolve 50 g of the reagent in 500 ml of distilled water
at 60° to 70°C. Make alkaline with 10 ml of sodium hydroxide solution,
2.2M. Bubble air that has been passed through a 10% sulfuric acid
solution through a tube which has been drawn into a capillary into the
solution while withdrawing air from the solution, which is contained in
a suction flask, under reduced pressure. Control the air flow so that
a rather vigorous bubbling through the solution is maintained. After
30 minutes of vigorous bubbling, cool the solution overnight in a re-
frigerator at about 4°C. Filter the crop of crystals through a No. 40
199
-------
(Nitrogen, Organic
+ Ammonia)
Whatman filter paper previously washed with ammonia-free water. Wash
the crystals repeatedly with ice-cold ammonia-free water until pH is
no longer basic. Dry the crystals at 60 to 70°C and store in a tightly
closed reagent bottle.
6.4 Sulfuric acid solution: Add slowly and with stirring 310 ml of reagent
grade, concentrated sulfuric acid to 600 ml of ammonia-free water.
Cool and dilute to 1.0 1.
6.5 Phenol solution: Dissolve 83 g of phenol in 500 ml of ammonia-free
water by stirring with a Teflon coated magnet for 10 minutes. Add 32 g
NaOH and dilute to 1 liter.
6.6 Sodium hypochlorite solution: Dilute 250 ml.of bleach solution contain-
ing a 5.25% NaOCl to 500 ml with ammonia-free water.
6.7 Neutralizing solution: Dissolve 6 g EDTA disodium salt and 65 g of
NaOH in 500 ml of distilled water. Dilute to 1.0 1.
6.8 Stock solution: Dissolve 4.7168 g of ammonium sulfate analytical reagent
in ammonia-free water and dilute to 1.0 1. 1.0 ml = 1.00 mg N.
6.9 Standard solution: Dilute 10.0 ml of stock solution to 100.0 ml.
1 ml = 0.10 mg N.
6.9.1 Using standard solution, prepare the following standards in
100-ml volumetric flasks:
mg N/l ml Standard Solution/100 ml
0.0 0
1.0 1.0
2.0 2.0
3.0 3.0
4.0 4.0
5.0 5.0
6.0 6.0
8.0 8.0
10.0 10.0
Note: Standards should be processed through complete procedure in same
manner as samples.
200
-------
- - (Nitrogen, Organic
+ Ammonia)
7. Procedure ,.'.,"• , .>': • ..,••;
7.1 Transfer a 25 ml sample of water to a 125 ml Erlenmeyer flask.
7.2 Add 3 ml of sulfuric acid solution and evaporate on a hot plate to
light fumes of SO,. This step may require approximately one hour. :. ,
Close attention is not required of the sample; however, it should not
be allowed to go 'to dryness. Cool the sample.
7,3 Add 1 ml of ammonia-free water and 1 g of potassium persulfate, low N,
and swirl the flask. .
7.4 Digest the sample on the hot plate for 15 minutes. Fumes of SO-
should begin coming off after 7 minutes. The samples should become clear
and transparent after this step, except in the presence of large amounts
i
of silica. Cool the sample; dilute to 25 ml with ammonia-free water.
The sample is now ready for automatic analysis.
7.5 Set up manifold as shown in Figure 1. ,
7.6 Allow both colorimeter and recorder to warm up for 30 minutes. : Run a
baseline with all reagents, feeding distilled water through the sample
line. Adjust dark current and operative opening on colorimeter to
obtain stable baseline.
7.7 Place distilled water wash tubes in alternate openings in Sampler and
set sample timing at 2.0 minutes.
7.8 Arrange standards in Sampler, in order of decreasing concentration.
Complete loading of Sampler tray with unknown samples from 7.4.
7.9 Switch sample line from distilled water to Sampler and begin analysis.
8. Calculation
8.1 Prepare standard curve by plotting peak heights of processed standards
against concentration values. Compute concentration of samples by
201
-------
(Nitrogen, Organic
+ Ammonia)
comparing sample peak heights with standard curve.
9. Precision and Accuracy
9.1 Precision and accuracy data are not available at this time.
References
1. E. C. Julian and R. C. Kroner, "Determination of Organic Nitrogen in Water
by Semi-Automatic Analysis," Automation in Analytical Chemistry, Technicon
Symposia, 1966, Vol. 1, Mediad Inc., White Plains, N.Y. (1967), p 542.
2, D. D. Van Slyke and A. J. Killer, Biol. Chem., 102, 499 (1933).
202
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-------
NTA
(Zinc-Zincon Method)
STORE! No: 00695
1. Scope and Application
1.1 In this method, NTA refers to the tri-sodium salt of nitrilotriacetic
acid, N(CH COONa)_.
w O
1.2 This method is applicable to surface waters in the range of 0.5 - 10.0
mg/1 NTA.
2. Summary of Method ^
2.1 Zinc forms a blue-colored complex with 2 carboxy-2'-hydroxy-5'-
sulfoformazylbenzene (Zincon) in a solution buffered to pH 9.2. When
NTA is added, the Zn-Zincon complex is broken which reduces the optical
density in proportion to the amount of NTA present.
3. Sample Handling and Preservation
3.1 Samples should be analyzed as soon as possible, as NTA has been shown
(2)
to be biodegradable
4 -r Interferences
4.1 Cations, such as calcium, magnesium, zinc, copper, iron, and manganese,
complex with NTA and give a negative interference. These ions are
removed by batch treating samples with ion-exchange resin. At concen-
trations higher than expected in typical river waters *• •*, only zinc,
copper, and iron were not completely removed with ion-exchange treat-
ment. Results are summarized in Table 1.
205
-------
TABLE 1
Interference of Common Metals
(NTA)
Metal
Blank
Zinc
Boron
Iron
Molybdenum
Manganese
Aluminum
Copper
Strontium
mg/1
added
0.0
2.0
5.0
5.0
2.0
4.0
3.0
0.5
5.0
1.0 mg/1
NTA
1.1
<0.5
1.1
0.95
1.0
1.1
0.85
<0.5
1.0
5.0 mg/1
NTA
Recoveries
5.5
0.6
5.5
4.6
5.5
5.6
5.2
3.4
5.4
4.2 This method has not been found applicable to salt waters.
Apparatus
5.1 Shaking machine, tray type, for stirring sample-resin mixtures in
125 ml Erlenmeyer flasks
5.2 Photometer, suitable for measurements at 620 nm.
Reagents
6.1 Sodium hydroxide, 6N: Dissolve 120 g NaOH in distilled water and
dilute to 500 ml.
6.2 Buffer: Dissolve 31 g boric acid and 37 g potassium chloride in
800 ml distilled water. Adjust pH to 9.2 with 6N NaOH. Dilute to
1 liter.
6.3 Hydrochloric acid, 2N: Dilute 83 ml concentrated HC1 to 500 ml with
distilled water.
6.4 Zinc: Dissolve 0.44 g ZnS04>7H 0 in 100 ml 2N HC1 and dilute to 1
liter with distilled water.
206
-------
(NTA)
6.5 Sodium Hydroxide, IN: Dissolve 4 g NaOH in distilled water and dilute
to 100 ml.
6.6 Zinc-Zincon: Dissolve 0.13 g Zincon (2-carboxy-2'-hydroxy-5'-
sulfoformazyl benzene) in 2 ml IN NaOH (6.5). Add 300 ml buffer (6.2),
While stirring, add 15 ml Zinc solution (6.4) and dilute to 1 liter
with distilled water.
6.7 Ion-Exchange Resin: Dowex 50W-X8, 50-100 mesh, Na* form (or equivalent).
6.8 Stock NTA Solution: Dissolve 1.0700 g N(CH COONa) .H-0 in distilled
2 3 *•
water and dilute to 1 liter. 1.0 ml = 1 mg NTA.
6.9 Working NTA Solution A: Dilute 10 ml Stock NTA solution (6.8) to 100 ml
with distilled water. 1 ml = 0.1 mg NTA. Prepare fresh daily.
6.10 Working NTA Solution B: Dilute 10 ml Working NTA Solution,A to 100 ml
with distilled water. 1 ml = 0.01 mg NTA.
7. Procedure '
7.1 Filter approximately 50 ml of well-mixed sample through a 0.45y
membrane filter.
7.2 Prepare a series of standards from 0.5 to 10 mg/1 NTA, including a blank
of distilled water. Treat standards and blank in same manner as filtered
samples.
7.3 To a 25 ml sample in a 125 ml Erlenmeyer flask add approximately 2.5 g
ion-exchange resin. Agitate sample for at least 15 minutes.
7.4 Filter through coarse filter paper to remove resin. Pipette 15 ml of
filtrate into a 50 ml beaker. Add 25 ml zinc-Zincon by pipette.
7.5 Read absorbance against distilled water at 620 run in a 1 cm or 2 cm cell.
8. Calculation
8.1 Prepare standard curve by plotting absorbance of standards vs. NTA
concentrations. Calculate concentrations of NTA, mg/1, directly from
this curve.
207
-------
(NTA)
9. Precision and Accuracy
9.1 In a single laboratory (AQC), using spiked surface water samples at
concentrations of 0.5, 2, 6, and 10 mg/1 NTA, standard deviations
were ±0.17, ±0.14, +0.1, and ±0.16, respectively.
9.2 In a single laboratory (AQC), using spiked surface water samples at
concentrations of 1.0 and 7.5 mg/1 NTA, recoveries were 120% and
103%, respectively.
REFERENCES
1. Thompson, J. E. and Duthie, J.R.,"The Biodegradability and Treatment of
NTA". Jour. WPCF, 40_, No. 2, 306 (1968).
2. Shumate, K. S. et al, "NTA Removal by Activated Sludge - Field Study".
ibid., 42_, No. 4, 631 (1970).
I ' • •
3. Kopp, J. F. and Kroner, R. C., "Trace Metals in Waters of the United States",
USDI, FWPCA, DPS, 1014 Broadway, Cincinnati, Ohio 45202.
208
-------
NTA
(Automated Zinc-Zincon Method)
STORE! No: 00695
1. Scope and Application
1.1 In this method, NTA refers to the tri-sodium salt of nitrilotriacetic
acid, N-(CH2COONa)3.
1.2 This method is applicable to surface waters in the range of 0.04 to
1.0 mg/1 and 0.5 to 10.0 mg/1 NTA, depending on which manifold system
is used. It does not apply to saline waters;, a positive interference
of 0.5 to 1.0 mg/1 is present in sewage-type samples.
1.3 Approximately 13 samples per hour can be analyzed.
2. Summary of Method j
I
j
2.1 Zinc forms a blue-colored complex with 2-carboxy-2'-hydroxy-5'-
sulfoformazylbenzene (Zincon) in a solution buffered to pH 9.2. When
NTA is added, the Zn-Zincon complex is broken which reduces the optical
density in proportion to the amount of NTA present.
3. Sample Handling and Preservation
3.1 Samples should be analyzed as soon as possible, as NTA has been shown
f2)
to be biodegradable. v
4. Interferences
4.1 Cations, such as calcium, magnesium, zinc, copper, iron, and manganese,
complex with NTA and give a negative interference. These ions are
removed automatically by passing the sample through an ion-exchange
(3)
column. At concentrations higher than expected in typical river waters,
only iron was not completely removed by this column treatment. Results,
summarized in Tables 1 and 2, show that iron gives a negative inter-
ference in concentrations above 3.0 mg/1 NTA.
209
-------
(NTA)
TABLE 1
Interference of Common Metals
Metal
Blank
Zinc
Iron*
Manganese
Copper
mg/1
added
0.0
2.0
5.0
4.0
0.5
1.0 mg/1
NTA
1.0
0.9
0.8
1.0
1.2
5.0 mg/1
NTA
Recoveries
5.0
4.9
3.8
4.9
4.9
TABLE 2
Effect of Iron on NTA Recovery in River Water
Iron Added
: mg/1
0.0
0.5
1.0
2.0
3.0
4.0
5.0
NTA Recovered, mg/1
(0.5 mg/1 added)
0.52
0.52
0.52
0.52
0.48
0.45
0.39
4.2 At concentration levels below 0.05 mg/1 NTA, negative peaking may occur
during analyses.
5. Apparatus
5.1 Technicon AutoAnalyzer consisting of:
5.1.1 Sampler I and II
5.1.2 Manifold
5.1.3 Proportioning pump
*See Table 2
210
-------
(NTA)
5.1.4 Colorimeter equipped with 15 mm tubular flow cell and 600 or
625 nm filter.
5.1.5 Recorder
6. Reagents
6.1 Sodium Hydroxide, 6N: Dissolve 120 g NaOH in distilled water and
dilute to 500 ml.
6.2 Buffer: Dissolve 31 g boric acid and 37 g potassium chloride in
800 ml distilled water. Adjust pH of solution to 9.2 with 6N NaOH.
Dilute to one liter.
6.3 Hydrochloride acid, 2N: Dilute 83 ml concentrated HC1 to 500 ml with
distilled water.!
6.4 Zinc: Dissolve 0.44 g ZnS04«7H20 in 100 ml 2N HC1. Dilute to one liter
with distilled water.
6.5 Sodium Hydroxide, IN: Dissolve 4 g NaOH in distilled water and dilute
to 100 ml.
6.6 Zinc-Zincon Reagent A (0.04-1.0 mg/1 NTA): Dissolve 0.065 g Zincon
powder (2-carboxy-2'-hydroxy-5'sulfoformazyl benzene) in 2 ml of IN
NaOH (6.5). Add 300 ml buffer (6.2). Place on a magnetic stirrer and
add 7.5 ml zinc solution (6.4). Dilute to one liter with distilled
water. This solution is stable for 12 hrs.
6.7 Zinc-Zincon Reagent B (0.5-10 mg/1 NTA): Dissolve 0.13 g Zincon in
2 ml IN NaOH (6.5). Stir on magnetic stirrer. Add 300 ml buffer (6.2)
and 15 ml zinc solution (6.4). Stir while mixing. Dilute to 1 liter
with distilled water. Stable for one week.
6.8 Ion-Exchange Resin, H+ Form: 20-50 mesh or 30-80 mesh, Dowex 50W-XB
or equivalent.
211
-------
(NTA)
NOTE: Column is prepared by sucking a water slurry of the resin into
12 inches of 3/16-inch OD sleeving. This may be conveniently done by
using a pipette and a loose-fitting glass wool plug in the sleeve.
6.9 Stock NTA Solution: Dissolve 1.0700 g of N(CH2CooNa) -H 0 in 500 ml
: of distilled water and dilute to one liter. 1 ml = 1.0 mg NTA.
6.10 Working Solution A: Dilute 10 ml of stock NTA solution to 100 ml
with distilled water. 1 ml = 0.1 mg NTA. Prepare daily.
6.11 Working Solution B: Dilute 10 ml of Solution A to 100 ml with
distilled water. 1 ml = 0.01 mg NTA. Prepare daily.
6.12 Working Solution C: Dilute 10 ml of Solution B to 100 ml with
distilled water. 1 ml = 0.001 mg NTA. Prepare daily.
6.13 Prepare a series of standards by diluting suitable volumes of working
solutions to 100.0 ml with distilled water. The following dilutions
are suggested:
ml of Solution C/100 ml Cone., mg NTA/1
2 0.02
4 0.04
6 0.06
8 0.08
10 0.10
ml of Solution B/100 ml
2 0.20
4 0.40
6 0.60
8 0.80
10 .1.00
ml of Solution A/100 ml
2 2.0
4 4.0
6 6.0
8 8.0
10 10.0
212
-------
(NTA)
7. Procedure
7.1 Set up manifold as shown in Figure 1.
7.2 Allow both colorimeter and recorder to warm up for 30 minutes. Run
a baseline with all reagents, feeding distilled water through the
sample line. Adjust dark current and operative opening on colorimeter
to obtain suitable baseline.
7.3 Place wash water tubes in sampler in sets of two, leaving every third
position vacant. Set sampling time at 1.5 minutes.
7.4 Place NTA standards in sampler in order of increasing or decreasing
concentration. Complete filling of sampler tray with unknown samples.
I
7.5 Switch sample line from distilled water to sampler and begin analysis.
i
8. Calculation
8.1 Prepare standard curve by plotting peak heights of processed NTA
standards against known concentrations. Compute concentration of samples
by comparing sample peak heights with standard curve.
9. Precision and Accuracy
9.1 In a single laboratory (AQC), using surface water samples at concen-
trations of 0.1, 0.18, 0.27, and 0.44 mg/1, the standard deviations were
±0.01, ±0.004, ±0.004, ±0.005, respectively. At concentrations of 1.3,
4.0, 5.8, and 7.4 mg/1, the standard deviations were ±0.05, ±0.05, ±0.07,
and ±0.1, respectively.
9.2 In a single laboratory (AQC), using surface water samples at concen-
trations of 0.18 and 0.27 mg/1, recoveries were 101% and 106%,
respectively. At concentrations of 4.0 and 5.8 mg/1, the recoveries
were 98% and 96%, respectively.
213
-------
(NTA)
References
1. Thompson, J. E. and Duthie, J. R., "The Biodegradability and Treatment
of NTA." Jour. WPCF, 40_, No. 2, 306 (1968).
2. Shumate, K. S. et al, "NTA Removal by Activated Sludge - Field Study."
ibid, 42_, No. 4, 631 (1970).
3. Kopp, J. F. and Kroner, R. C., "Trace Metals in Waters of the United States."
USDI, FWPCA, DPS, 1014 Broadway, Cinti, Ohio 45202.
214
-------
N)
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-------
1. Scope and Application
OIL AND GREASE
STORE! NO. 00550
1.1 This method includes the measurement of hexane extractable matter
from waters, industrial wastes, and sewages. It is applicable to the
determination of relatively non-volatile hydrocarbons, animal fats
and waxes, grease and other types of greasy-oily matters.
1.2 The method is not applicable to measurement of light hydrocarbons that
volatilize at temperatures below 80°C.
1.3 The method covers the range from 5 to 1000 mg/1 of extractable material.
2. Summary of Method
2.1 The sample is acidified to a low pH (<3) and extracted with hexane
using a Soxhletj extraction. The solvent is evaporated from the separated
i
extract and the! residue weighed.
3. Definitions
3.1 The definition of grease and oil is based on the procedure used. The
source of the oil and/or grease, the solvent used, and presence of ex-
tractable non-oily matter will influence the material measured and
interpretation of results.
4. Purity of Reagents
4.1 Reagent grade hexane shall be used.
5. Sampling and Storage
5.1 A representative sample should be collected in a wide-mouth bottle
marked at the 1 liter volume. The initial step of acidification shall
be carried out in the sample bottle. The entire sample is used for
the test.
5.2 Because losses of grease will occur on sampling equipment, collection
of a composite sample is impractical, and the examination of individual
217
-------
(Oil and Grease)
portions collected at prescribed time intervals must be used to obtain
the average concentration over an extended period.
6. Apparatus
6.1 Extraction apparatus consisting of:
6.1.1 Soxhlet Extractor, medium size (Corning No. 3740 or equivalent).
6.1.2 Soxhlet thimbles, to fit in Soxhlet Extractor, 6.1.1.
6.1.3 Flask, 125 ml (Corning No. 4100 or equivalent).
6.1.4 Condenser, Allihn (bulb) type, to fit extractor.
6.2 Vacuum pump, or other source of vacuum.
6.3 Buchner funnel, 12 cm.
7. Reagents
7.1 Sulfuric acid, 1:1. Mix equal volumes of cone. H_SO. and distilled water.
7.2 Hexane, b.p. 69°C.
7.3 Filter paper, Whatman No. 40, 11 cm.
7.4 Muslin cloth discs, 11 cm (muslin cloth available at sewing centers).
7.5 Diatomaceous - silica filter aid suspension, 10 g/1 distilled water.
Note 1 - Hyflo Super-Gel (Johns-Manvilie Corp.) or equivalent is used
in the preparation of the filter aid suspension.
8. Procedure
8.1 In the following procedure, all steps must be rigidly adhered to if
consistent results are to be obtained.
8.2 Acidify the 1 liter sample with 1:1 H-SO. to a pH below 3. For most samples
about 2 ml of the 1:1 acid will be sufficient. Use of a pH sensitive
paper is recommended when checking the pH of the sample to avoid possible
loss of oil and grease by adherence to glass electrodes.
Note: If the sample has been acidified in the field at the time of
collection this step may be omitted.
218
-------
(Oil and Grease)
8.3 Prepare a filter consisting of a muslin cloth disc overlaid with
filter paper. Place the assembled filter in the Buchner funnel and
wet the filter, pressing down the edges to secure a seal. Using a vac-
uum, add 100 ml of the filter aid suspension through the filter and
then wash with 3-100 ml volumes of distilled water. Continue the
vacuum until no more water passes through the filter.
8.4 Filter the acidified sample under vacuum and again continue the vacuum
until no more water passes through the filter.
8.5 Remove the filter paper from the funnel with a pair of forceps and
carefully place in the Soxhlet thimble. Wipe the sides and bottom
of the collecting vessel, the stirring rod, and the Buchner funnel with
pieces of filter, paper soaked in hexane. Add all pieces of filter
paper to the thimble. In general, care must be taken to remove all
grease and oil films and to collect all solid material for placement in
the thimble.
8.6 Dry the extraction thimble containing the filter paper in an oven at
103°C for exactly 30 minutes. Fill the thimble with small glass beads
or glass wool.
8.7 Weigh the extraction flask (pre-dried in oven at 105°C and stored in
desiccator), add the hexane, and connect to the Soxhlet apparatus in
which the extraction thimble has been placed. Extract at the rate of
20 cycles per hour for four hours. The four hours is timed from the first
cycle.
8.8 Distill the solvent from the extraction flask in a water bath at 85°C.
Dry by placing the flask on a steam bath and draw air through the flask
by means of an applied vacuum for 15 minutes.
219
-------
(Oil and Grease)
8.9 Cool in a desiccator for 30 minutes and weigh.
9. Calculation
n n ,, . . , mg increase in weight of flask x 1,000
9.1 mg/1 total grease = -& mi sLple l
10. Precision and Accuracy
10.1 Precision and accuracy data are not available.
220
-------
ORGANIC CARBON NliffiERS.
(Total and Dissolved) TOTAL: 00680
DISSOLVED: 00681
1. Scope and Application ~~r
1.1 This method includes the measurement of organic carbon in surface
waters, domestic and industrial wastes, and saline waters. Ex-
clusions are noted under Definitions and Interferences.
1.2 The method is applicable to measurement in the range of 1 to
150 mg/liter.
2. Summary of Method
2.1 A micro sample of the wastewater to be analyzed is injected into
a catalytic combusion tube which is enclosed by an electric furnace
thermostated at 950°C. The water is vaporized and the carbonaceous
i
material is oxidized to carbon dioxide (CO,,) and steam in a carrier
stream of pure oxygen or air. The oxygen flow carries the steam and
C02 out of the furnace where the steam is condensed and the condensate
removed. The C02, oxygen, and remaining water vapor enter an infrared
analyzer sensitized to provide a measure of CO-. The amount of CO™
present is directly proportional to the concentration of carbonaceous
material in the injected sample.
3. Definitions
3.1 The carbonaceous analyzer measures all of the carbon in a sample
after injection into the combustion tube. Because of various properties
of carbon-containing compounds in liquid samples, preliminary treat-
ment of the sample prior to injection dictates the definition of the
carbon as it is measured.
Forms pf carbon that are measured by the combustion-infrared method
are:
221
-------
(Organic Carbon)
A) soluble, nonvolatile organic carbon; for instance,
natural sugars.
B) soluble, volatile organic carbon; for instance, mercaptans.
C) insoluble, partially volatile carbon; for instance, oils.
D) insoluble, particulate carbonaceous materials, for
instance, cellulose fibers.
E) soluble or insoluble carbonaceous materials adsorbed or
entrapped on insoluble inorganic suspended matter; for
instance, oily matter adsorbed on silt particles.
3.2 The final usefulness of the carbon measurement is in assessing the
potential oxygen-demanding load of organic material on a receiving
stream. This statement applies whether the carbon measurement is
made on a sewage plant effluent, industrial waste, or on water taken
directly from the stream. In this light, carbonate and bicarbonate
carbon are not a part of the oxygen demand in the stream and there-
fore should be discounted in the final calculation or removed prior
to analysis. The manner of preliminary treatment therefore defines
the types of carbon which are measured.
4. Sample Handling and Preservation
4.1 Sampling and storage of samples in glass bottles is preferable.
Sampling and storage in plastic bottles such as conventional poly-
ethylene and cubitainers is permissible if it is established that
the containers do not contribute contaminating organics to the
samples (Note 1).
Note 1 - A brief study performed in the AQC Laboratory indicated
that distilled water stored in new, one quart cubitainers did not
show any increase in organic carbon after two weeks exposure.
222
-------
(Organic Carbon)
4.2 Because of the possibility of oxidation or bacterial decomposition
of some components of aqueous samples, the lapse of time between
collection of samples and start of analysis should be kept to a
minimum. Also, samples should be kept cool (4°C) and protected
from sunlight and atmospheric oxygen.
4.3 In instances where analysis cannot be performed within two hours
(2 hours) from time of sampling, it is recommended that the sample be
acidified (pH = 2) with HC1 or H2S04.
5. Interferences
5.1 Carbonate and bicarbonate carbon represent an interference under
the terms of this test and must be removed or accounted for in the
I
final calculation.
5.2 This procedure is applicable only to homogeneous samples which can
be injected into the apparatus reproducibly by means of a microliter
type syringe. The needle openings of the syringe limit the maximum
size of particles which may be included in the sample. (Cf 6.3)
6. Apparatus
6.1 Apparatus for blending or homogenizing samples:
Generally, a Waring-type blender is satisfactory.
6.2 Apparatus for total and dissolved organic carbon:
6.2.1 Dow-Beckman Carbonaceous Analyzer, (single channel) or
6.2.2 Dow-Beckman Carbonaceous Analyzer Model No. 915 (dual
channel).
6.3 Hypodermic syringe, 0-50 ul, needle opening of approximately
150 microns; Hamilton No. 705 N or equivalent is satisfactory.
6.3,1 Hamilton No. 750 N, 0-500 yl has a needle opening of approxi-
mately 400 microns and may be used for samples containing large
223
-------
(Organic Carbon)
particulates.
6.3.2 Hamilton No. CR-700-20 for 20 pi size and No. CR-700-200
for 200 yl size, needle point style No. 3, are push button
syringes which insure uniformity of injection rate.
7. Reagents and Materials
7.1 Distilled water used in preparation of standards and for dilution
of samples should be ultra pure to reduce the size of the blank.
Carbon dioxide-free, double distilled water is recommended. Ion
exchanged waters are not recommended because of the possibility of
, contamination with organic materials from the resins.
7.2 Potassium Hydrogen Phthalate, stock solution, 1000 mg carbon/liter:
Dissolve 0.2128 g of potassium hydrogen phthalate (Primary Standard
Grade) in double distilled water and dilute to 100.0 ml.
Note: Sodium oxalate and acetic acid are not recommended as stock
solutions.
7.3 Potassium Hydrogen Phthalate, standard solutions: Prepare standard
solutions from the stock solution with double distilled water as
follows:
ml of Stock Solution Standard
Diluted to 100 ml mg C/liter
1.0 10
2.0 20
3.0 30
4.0 40
5.0 50
6.0 60
8.0 80
10.0 100
7.4 Carbonate-bicarbonate, stock solution, 1000 mg carbon/liter: Weigh
0.3500 g of sodium bicarbonate and 0.4418 g of sodium carbonate
and transfer both to the same 100 ml volumetric flask. Dissolve with
224
-------
(Organic Carbon)
double distilled water.
7.5 Carbonate-bicarbonate, standard solution: Prepare a series of
standards similar to 7.3.
7.6 Blank solution: Use the same distilled water (or similar quality
water) used for the preparation of the standard solutions.
7.7 Packing for total carbon tube. Dissolve 20 g of Co(N0_)2.6H~0
(cobalt nitrate hexahydrate) in 50 ml of distilled water. Add this
solution to 15 grams of long-fiber asbestos in a porcelain evaporating
dish. Mix and evaporate to dryness on a steam bath. Place the dish
in a cold muffle furnace and bring to a temperature of 950°C. After
one to two hours at this temperature, remove the dish and allow to
cool. Break up any large lumps and mix adequately but not excessively.
With the combustion tube held in a vertical position, taper joint up,
put about 1/2" of untreated asbestos in the tube first, then transfer,
in small amounts, approximately one gram of catalyst into the tube
with forceps or tweezers. As it is added, tap or push the material
gently with a 1/4" glass rod. Do not force the packing. The weight
of the rod itself is sufficient to compress the material. When
completed, the length of the packing should be about five or six
centimeters. Test the packed tube by measuring the flow rate of
gas through it at room temperature, and then at 950°C. The rate
should not drop more than 20%.
7.8 Packing for carbonate tube, (dual channel instrument). Place a small
wad of quartz wool or asbestos near the exit end of the carbonate
evolution tube. From the entrance end add 6-12 mesh quartz chips,
allowing these to collect against the wad to a length of 10 cm. Pour
225
-------
(Organic Carbon)
an excess of 85 percent phosphoric acid into the tube while holding
it vertically, and allow the excess to drain out.
8. Instrument Adjustment
8.1 Turn on the infrared analyzer, recorder, and tube furnances, setting
the total carbon furnace at 950°C and the carbonate furnace at 175°C.
Allow a warm-up time of at least 2 hr. for attainment of stable
operation; in daily use the analyzer can be left on continuously.
Adjust the oxygen flow rate to 80 to 100 ml/min through the total
carbon tube. With the recorder set at the appropriate mv range,
adjust the amplifier gain so that a 20-nl sample of the 100 mg/liter
carbon standard gives a peak height of approximately half the recorder
scale (see 7.3). At this setting the noise level should be less than
0.5 percent of full scale. If the noise level is higher, the analyzer
or the recorder may require servicing.
8.1.1 Single channel unit may be equipped with a large-diameter com-
bustion tube and the dual channel unit with a Hastalloy tube for
the total carbon channel. In such cases, a 100-yl sample may be
injected and appropriate standards in the range of 1 to 30
mg/1 carbon used.
9. Calibration - Dual Channel Instrument
9.1 Successively introduce 20 yl of each phthalate standard into the
total carbon tube and read the height of the corresponding peak.
Between injections allow the recorder pen to return to its base line.
The actual injection technique is as follows: Rinse the syringe
several times with the solution to be analyzed, fill, and adjust to
20 yl. Wipe off the excess with soft paper tissue, taking care that
226
-------
(Organic Carbon)
no lint adheres to the needle. Remove the plug from the syringe
holder, insert the sample syringe, and inject the sample into
the combusion tube with a single, rapid movement of the index
finger. Leave the syringe in the holder until the flow rate returns
to normal, then replace it with the plug. Run duplicate determinations
on each solution and on a water blank.
9.2 Correct standards for blank correction as follows: Standard peak
height minus blank peak height = correct peak height in mm. Prepare
a standard curve of total carbon versus peak height.
9.3 In the same way, prepare a series of diluted carbonate standards
containing 20, 40, 60, 80, and 100 mg of inorganic carbon per liter.
Turn the four-rway valve of the apparatus to direct the gas flow
through the low temperature tube and to the analyzer. Adjust the flow
rate to 80 to 100 ml/min and allow the baseline to become stabilized.
Successively introduce 20 pi of each standard and a water blank in
duplicate into the low temperature tube and read the peak heights as
previously described.
9.4 Prepare a standard curve of inorganic carbon versus peak height
applying the correction as noted in 9.2.
10. Procedure - Dual Channel Instrument - Unpreserved samples.
10.1 Mix or blend each sample thoroughly and carry out any appropriate
dilution to bring the carbon content within the range of the standard
curve.
10.2 Following the technique described in 9.1 and 9.3, inject 20-pl
samples successively (in duplicate) into each tube and read the peak
heights corresponding to total carbon and inorganic (carbonate) carbon.
227
-------
(Organic Carbon)
From the appropriate calibration curve and each peak height
observed, read the corresponding carbon concentration in mg/liter.
10.3 Substract the inorganic carbon value from the total carbon value.
The difference thus obtained is operationally defined as Total
Organic Carbon. These values may be different from values obtained
on acid-blown samples. Results may be verified by operating the
unit as a single channel system, i.e., injecting an acidified
nitrogen-purged sample into the high temperature furnace side and
comparing results.
10.4 Filter a 100 ml aliquot through a pre-rinsed 0.45 p pore size filter.
Repeat sample injection as in 10.2.
10.5 Subtract the dissolved inorganic carbon value from the dissolved
carbon value. The difference thus obtained is operationally defined
as Dissolved Organic Carbon. These values may be different from
values obtained on acid-blown samples. Results may be verified by
operating the unit as a single channel system, i.e., injecting an
acidified nitrogen-purged sample into the high temperature furnace
side and comparing results.
11. Calibration - Single Channel Instrument
11.1 Standardize the instrument according to directions given in 9.1 and
9.2.
12. Procedure - Single Channel Instrument
12.1 Transfer a representative aliquot of about 10 - 15 ml to a 30 ml
beaker. If not already acid preserved, add 2 or more drops of con-
centrated HC1 until the pH is reduced to = 2 and purge with C02
nitrogen gas for about 5-10 minutes (do not use plastic tubing).
228
-------
13.
(Organic Carbon}
Place the beaker on a magnetic stirrer and while stirring withdraw
a 20 ul sample. Inject the sample as in 9.1.
12.2 Obtain concentration directly from standard curve. The carbon thus
measured is operationally defined as Total Organic Carbon.
12.3 Filter a 100 ml aliquot through a pre-rinsed 0.45 y pore size filter
and proceed as in 12.1.
12.4 Obtain concentration directly from standard curve. The carbon thus
measured is operationally defined as Dissolved Organic Carbon.
Precision and Accuracy
13.1 Twenty-eight analysts in twenty-one laboratories analyzed distilled
water solutions containing exact increments of oxidizable organic
compounds, with the following results:
Increment as
TOC
mg/liter
Precision as
Standard Deviation
TOC, mg/liter
Accuracy as
Bias,
Bias,
mg/liter
4.9
107
3.93
8.32
+15.27 + .75
+ 1.01 +1.08
(FWQA Method Study 3, Demand Analyses)
229
-------
pH
STORE! Number: 00400
1. Scope and Application
1.1 This method is applicable to drinking waters and surface waters,
domestic and industrial wastes, and saline waters.
2. Summary of Method
2.1 The pH of a sample is an electrometric measurement, using either
a glass electrode in combination with a reference potential
(saturated calomel electrode) or a combination electrode (glass
and reference).
3. Comments
3.1 The sample must be analyzed as soon as practical; preferably within
a few hours. Do not open sample bottle before analyses.
3.2 Oil and greases, by coating the pH electrode, may interfere by
causing sluggish response.
3.3 At least three buffer solutions must be used to initially standardize
the instrument. They should cover the range of pH of the samples
to be measured.
3.4 Field pH measurements using comparable instruments are reliable.
4. Precision and Accuracy
4.1 Forty-four analysts in twenty laboratories analyzed six synthetic
water samples containing exact increments of hydrogen-hydroxyl ions,
with the following results:
230
-------
CpH)
Increment as
pH Units
3.5
3.5
7.1
7.2
8.0
8.0
Precision as
Standard Deviation
pH Units
0.10
0.11
0.20
0.18
0.13
0.12
Accuracy
Bias,
%
-0.29
-0.00
+1.01
-0.03
-0.12
+0.16
as
Bias,
pH Units
-0.01
—
+0.07
-0.002
-0.01
+0.01
(FWPCA Method Study 1, Mineral and Physical Analyses)
4.2 In a single laboratory (AQC), using surface water samples at an
average pH of 7.7, the standard deviation was ±0.1.
5. Reference
5.1 The procedure to be used for this determination is found in:
\
Standard Methods for the Examination of Water and Wastewater,
13th Edition, p. 276, Method 144A (1971).
ASTM Standards, Part 23, Water; Atmospheric Analysis, p. 280,
Method D1293-65 (1970).
231
-------
PHENOLICS
(4-AAP Method With Distillation)
STORET NO. 32730
1. Scope and Application
1.1 This method is applicable to the analysis of drinking waters,
surface waters, domestic and industrial wastes and saline waters.
1.2 The method is capable of measuring phenolic materials from
about 5 yg/1 to about 1000 yg/1 when the colored end product is
extracted and concentrated in a solvent phase using phenol as a
standard.
1.3 The method is capable of measuring phenolic materials from about
SO yg/1 to about 5000 yg/1 in the aqueous phase (without solvent
extraction) using phenol as a standard.
1.4 It is not possible to use this method to differentiate between
different kinds of phenols.
2. Summary of Method
2.1 Phenolic materials react with 4-aminoantipyrine in the presence of
potassium ferricyanide at a pH of 10 to form a stable reddish-
brown colored antipyrine dye. The amount of color produced is a
function of the concentration of phenolic material.
3. Comments
3.1 For most samples a preliminary distillation is required to remove
interfering materials.
3.2 Color response of phenolic materials with 4-aminoantipyrine is
not the same for all compounds. Because phenolic type wastes
232
-------
(Phenolics)
usually contain a variety of phenols, it is not possible to
duplicate a mixture of phenols to be used as a standard. For
this reason phenol itself has been selected as a standard and
any color produced by the reaction of other phenolic compounds is
reported as phenol. This value will represent the minimum con-
centration of phenolic compounds present in the sample.
3.3 Control of the pH of the reaction may be accomplished using
the procedure detailed in Standard Methods (Page 506, 13th
Edition) or ASTM, Part 23, Page 523 (Nov. 1970) or by the use
of the ammonium hydroxide-ammonium chloride buffer used in the
water hardness test Standard Methods, 13th Edition, Page 181,
(1971). !
I
4. Precision and Accuracy
4.1 Using the extraction procedure for concentration of color, six
laboratories analyzed samples at concentrations of 9.6, 48.3
and 93.5 yg/1. Standard deviations were, respectively, 0.99,
3.1 and 4.2 yg/1.
4.2 Using the direct photometric procedure, six laboratories analyzed
samples at concentrations of 4.7, 48.2 and 97.0 mg/1.
4.3 American Society for Testing and Materials, Part 23, pp. 524-525
Method D-1783-70 (1970).
233
-------
(Phenolics)
5. References
The procedure to be used for this determination is found in:
Standard Methods for the Examination of Water and Waste-
water, 13th Edition, pp. 501-510, Method No. 222 through
222E (1971).
American Society for Testing and Materials, Part 23,
pp. 519-525, Method D-1783-70 (1970).
234
-------
PHOSPHORUS, ALL FORMS
(Single Reagent Method) STORET NO:
SEE TABLE 1
1. Scope and Application
1.1 These methods cover the determination of specified forms of phosphorus
in surface waters, domestic and industrial wastes, and saline waters.
They may be applicable to sediment-type samples, sludges, algal blooms,
etc., but sufficient data is not available at this time to warrant such
usage when measurements for phosphorus content are required.
1.2 The methods are based on reactions that are specific for the ortho-
phosphate ion. Thus, depending on the prescribed pre-treatment of the
sample, the various forms of phosphorus given in Figure 1 may be determined.
These forms are, in turn, defined in Table 1.
1.2.1 Except for in-depth and detailed studies, the most commonly
measured forms are phosphorus and dissolved phosphorus, and ortho-
phosphate and(dissolved orthophosphate. Hydrolyzable phosphorus
is normally found only in sewage-type samples and insoluble forms
of phosphorus, as noted, are determined by calculation.
1.3 The methods are usable in the 0.01 to 0.5 mg/1 P range.
2. Summary of Method
2.1 Ammonium molybdate and potassium antimonyl tartrate react in an acid
medium with dilute solutions of phosphorus to form an antimony-phospho-
molybdate complex. This complex is reduced to an intensely blue-colored
complex by ascorbic acid. The color is proportional to the phosphorus
concentration.
2.2 Only orthophosphate forms a blue color in this test. Polyphosphates (and
some organic phosphorus compounds) may be converted to the orthophosphate
form by sulfuric-acid-hydrolysis. Organic phosphorus compounds may be
235
-------
NJ
w
c\
Residue
SAMPLE
Total Sample (No Filtration)
V
Direct
Colorimetry
Hydrolysis
_\ r Pn 1 iyg_i ffl^n
Orthophosphate
Hydrolyzable §
Orthophosphate
Filter (through 0.45 p membrane filter)
\/
\/
Filtrate
>
Direct
Colorimetry
/
Dissolved
Orthophosphate
s
H2S04
Hydrolysis §
i Colorimetry .
Diss. Hydrolyzable
§ Orthophosphate
Persulfate
Digestion §
.Colorimetry
Dissolved
Phosphorus
Persulfate
Digestion
Phosphorus
Figure 1. Analytical Scheme for Differentiation of Phosphorus Forms.
-------
(Phosphorus)
converted to the orthophosphate form by sulfuric-acid-hydrolysis.
Organic phosphorus compounds may be converted to the orthophosphate
(2i
form by persulfate digestion. *• '
3. Definitions
3.1 The various forms of phosphorus are defined in Table 1.
4. Sampling Handling and Preservation
4.1 If benthic deposits are present in the area being sampled, great care
should be taken not to include these deposits.
4.2 Sample containers may be of plastic material, such as cubitainers, or
.of Pyrex glass.
4.3 If the analysis cannot be performed the same day of collection, the
sample should be preserved by the addition of 40 mg HgCl- per liter and
refrigeration at 4°C. Note HgCl- interference under 5.4.
238
-------
(Phosphorus)
TABLE 1 .
PHOSPHORUS TERMINOLOGY
1. Phosphorus (P) - all of the phosphorus present in the sample, regardless
of form, as measured by the persulfate digestion procedure. (00665)
a. Orthophosphate (P, ortho) - inorganic phosphorus [(P04)~ ] in the sample
as measured by the direct colorimetric analysis procedure. (70507)
b. Hydrolyzable Phosphorus (P, hydro) - phosphorus in the sample as
measured by the sulfuric acid hydrolysis procedure, and minus pre-
determined orthophosphates. This hydrolyzable phosphorus includes poly-
"
phosphates [(PoO-)" , (P30^o)~> etc.] + some organic phosphorus. (00669)
c. Organic Phosphorus (P, org) - phosphorus (inorganic + oxidizable organic)
in the sample as measured by the persulfate digestion procedure, and
minus hydrolyzable phosphorus and orthophosphate . (00670)
2. Dissolved Phosphorus (P-D) - all of the phosphorus present in the filtrate
of a sample filtered through a phosphorus -free filter of 0.45 micron pore
size and measured by the persulfate digestion procedure. (00666)
a. Dissolved Orthophosphate (P-D, ortho) - as measured by the direct color-
imetric analysis procedure. (00671)
b. Dissolved Hydrolyzable Phosphorus (P-D, hydro) - as measured by the
sulfuric acid hydrolysis procedure and minus pre-determined dissolved
orthophosphates . (00672)
c. Dissolved Organic Phosphorus (P- D, org) - as measured by the persulfate
digestion procedure, and minus dissolved hydrolyzable phosphorus and
orthophosphate. (00673)
3. The following forms, when sufficient amounts of phosphorus are present in
the sample to warrant such consideration, may be calculated:
239
-------
(Phosphorus)
TABLE 1 (Continued)
a. Insoluble Phosphorus (P-I) = (P) - (P-D). (00667)
*
(1) Insoluble orthophosphate (P-l, ortho) = (P, ortho) - (P-D, ortho). (00674)
(2) Insoluble Hydrolyzable Phosphorus (P-I, hydro) = (P, hydro) -
(P-D, hydro). (00675)
(3) Insoluble Organic Phosphorus (P-I, org) = (P, org) - (P-D, org).(00676)
4. All phosphorus forms shall be reported as P, mg/1 , to the third place.
5. Interferences
5.1 It is reported (1) that no interference is caused by copper, iron, or
silicate at concentrations many times greater than their greatest re-
ported concentration in sea water. However, high iron concentrations
can cause precipitation of phosphorus through the formation of clumps
in the bottom of the sample.
i
5.2 The salt error forisamples ranging from 5 to 20 percent salt content was
i
\
found to be less than 1 percent(l).
5.3 Arsenate, in concentrations greater than found in sea water, does not
interfere*-1'.
5.4 Mercury chloride, used as a preservative, interfers when the chloride
level of the sample is low (<50 mg cl/l). This interference is overcome
by spiking samples with a minimum of 50 mg/1 of sodium chloride.
6. Apparatus
6.1 Photometer - A spectrophotometer or filter photometer suitable for
measurements at 880 nm, and providing a light path of 1 inch (2.54 cm)
or longer, should be used.
240
-------
(Phosphorus)
6.2 Acid-washed glassware: All glassware used in the determination should
be washed with hot '1:1"HCVand rinsed with distilled water. The acid-
washed glassware should be filled with distilled water and treated with
all the reagents to remove the'last traces of phosphorus that might be
adsorbed on the glassware. Preferably, this glassware should be used
only for the determination of phosphorus and after use it should be
rinsed with distilled water and kept covered until needed again. If
this is done, the treatment with 1:1 HC1 and reagents is only required
occasionally. Commercial detergents should never be used.
7. Reagents
7.1 Sulfuric acid solution, 5N: Dilute 70 ml of cone. H2SO. with distilled
water to 500 ml.
7.2 Potassium antimonyl tartrate solution: Weigh 1.3715 g K(SbO)C4H406.
1/2 H20, dissolve in 400 ml distilled water in 500 ml volumetric flask,
dilute to volume. Store at 4°C in a dark, glass-stoppered bottle.
7.3 Ammonium molybdate solution: , Dissolve 20 g (NH.)^07024.4H.-0 in 500 ml
distilled water. Store in a plastic bottle at 4°C.
7.4 Ascorbic acid, 0.1M: Dissolve 1.76 g of ascorbic acid in 100 ml of
distilled water. The solution is stable for about a week if stored at
4°C.
7.5 Combined reagent: Mix the above reagents in the following proportions
for 100 ml of the mixed reagent: 50 ml of 5N H2S04, 5 ml of potassium
antimonyl tartrate solution, 15 ml of ammonium molybdate solution, and
30 ml of ascorbic acid solution. Mix after addition of each reagent.
241
-------
(Phosphorus)
All reagents must reach room temperature before they are mixed and
must be mixed in the order given. If turbidity forms in the
combined reagent, shake and let it stand for a few minutes until the
turbidity disappears before processing. The reagent is stable for
one week if stored at 4°C.
7.6 Strong-acid solution: Slowly add 310 ml cone. H-SCK to 600 ml dis-
tilled water. When cool, dilute to 1 liter.
7.7 Ammonium persulfate.
7.8 Stock Solution: Dissolve in distilled water 0.2197 g of potassium
dihydrogen phosphate, KH PO., which has been dried in an oven at
105°C. Dilute the solution to 1.0 1; 1.00 ml equals 0.05 mg P.
7.9 Standard Solution: Dilute 10.0 ml of stock phosphorus solution to
1.0 1 with distilled water; 1.00 ml equals 0.5 yg P.
7.9.1 Using standard solution, prepare the following standards
in 50.0 ml volumetric flasks:
ml of Standard Solution Cone., mg/1
0
1.0
3.0
5.0
10.0
20.0
30.0
40.0
50.0
0.00
0.01
0.03
0.05
0.10
0.20
0.30
0.40
0.50
8. Procedure
8.1 Phosphorus
8.1.1 Add 1 ml of strong-acid solution to a 50 ml sample in a
125-ml Erlenmeyer flask.
242
-------
(Phosphorus)
8.1.2 Add 0.4 gram of ammonium persulfate.
8.1.3 Boil gently on a pre-heated hot plate for approximately
30-40 minutes or until a final volume of about 10 ml is
reached. Do not allow sample to go to dryness. Alter-
natively, heat for 30 minutes in an autoclave at 121°C
(15-20 psi).
8.1.4 Add phenolphathalein and adjust sample to pink with IN NaOH.
Bring back to colorless with one drop of strong acid solution.
Cool and dilute the sample to 50.0 ml. If sample is not clear
at this point, filter.
8.1.5 Determine phosphorus as outlined in 8.3.2 Orthophosphate.
8.2 Hydrolyzable Phosphorus
8.2.1 Add 1 ml of strong-acid solution to a 50-ml sample in a. 125-ml
Erlenmeyer flask.
8.2.2 Boil gently on a pre-heated hot plate for 30-40 minutes or until
a final volume of about 10 ml is reached. Do not allow sample
to go to dryness. Alternatively, heat for 30 minutes in an
autoclave at 121°C (15-20 psi).
8.2.3 Add phenolphthalein and adjust sample to pink with 1 N NaOH.
Bring back to colorless with one drop strong-acid solutions. Cool
and dilute the sample to 50 ml.
8.2.4 The sample is now ready for determination of phosphorus as outlined
in 8.3.2 Orthophosphate.
8.3 Orthophosphate
8.3.1 Add 1 drop of phenolphthalein indicator to the 50.0 ml sample.
If a red color develops, add strong-acid solution drop-wise
to just discharge the color.
243
-------
(Phosphorus)
8.3.2 Add 8.0 ml of combined reagent to sample and mix thoroughly.
After a minimum of ten minutes, but no longer than thirty
minutes, measure the color absorbance of each sample at 880
nm with a spectrophotometer, using the reagent blank as the
reference solution.
9. Calculation
9.1 Prepare standard curve by plotting absorbance values of standards
as ordinates and the corresponding phosphorus concentrations as abscissas.
9.1.1 Process standards and blank exactly as the samples. Run at
least a blank and two standards with each series of samples. If
the standards do not agree within *2% of the true value,
prepare a new calibration curve.
9.2 Obtain concentration value of sample directly from prepared standard
curve. Report results as P, mg/1.
10. Precision and Accuracy 1
10.1 Thirty-three analysts in nineteen laboratories analyzed natural water
samples containing exact increments of organic phosphate, with the
following results:
Increment as
Total Phosphorus
rag P/liter
0.110
0.132
0.772
0.882
Precision as
Standard Deviation
mg P/liter
0.033
0.051
0.130
0.128
Accuracy
Bias,
% mg
+ 3.09
+11.99
+ 2.96
- 0.92
as
Bias,
P/liter
+ .003
+ .016
+ .023
-.008 ,
(FWPCA Method Study 2, Nutrient Analyses).
10.2 Twenty-six analysts in sixteen laboratories analyzed natural water
samples containing exact increments of orthophosphate, with the
following results:
244
-------
(Phosphorus)
Increment as
Orthophosphate
mg P/liter
0.029
0.038
0.335
0.383
Precision as
Standard Deviation
mg P/liter
0.010
0.008
0.018
0.023
Accuracy
Bias,
% mg
-4.95
-6.00
-2.75
-1.76
as
Bias,
P/liter
.001
.002
.009
.007
(FWPCA Method Study 2, Nutrient Analyses)
References
1. J. Murphy and J. Riley, "A Modified Single Solution Method for the
Determination of Phosphate in Natural Waters." Anal. Chim. Acta., 27, 31
(1962).
2. M. Gales, Jr., E. Julian, and R. Kroner, "Method for Quantitative Deter-
mination of Total Phosphorus in Water." Jour AWWA, 58, No. 10, 1363 (1966)
245
-------
PHOSPHORUS, ALL FORMS
(Automated Single Reagent Method) STORE! NO-
SEE TABLE 1
1. Scope and Application
1.1 These methods cover the determination of specified forms of phosphorus
in surface waters, domestic and industrial wastes, and saline waters.
They may be applicable to sediment-type samples, sludges, algal blooms,
etc., but sufficient data is not available at this time to warrant such
usage when measurements for phosphorus content are required.
1.2 The methods are based on reactions that are specific for the ortho-
phosphate ion. Thus, depending on the prescribed pre-treatment of
the sample, the various forms of phosphorus given in Figure 1 may be
determined. These forms are, in turn, defined in Table 1.
1.2.1 Except for in-depth and detailed studies, the most commonly
measured forms are phosphorus and dissolved phosphorus, and
orthophosphate and dissolved orthophosphate. Hydrolyzable
phosphorus is normally found only in sewage-type samples and
insoluble forms of phosphorus, as noted, are determined by
calculation.
1.3 The methods are usable in the 0.01 to 1.0 mg P/l range. Approximately
20 samples per hour can be analyzed.
2. Summary of Method
2.1 Ammonium molybdate and potassium antimonyl tartrate react in an acid
medium with dilute solutions of phosphorus to form an antimony-ph.osph.o-
molybdate complex. This complex is reduced to an intensely blue-colored
complex by ascorbic acid. The color is proportional to the phosphorus
concentration.
246
-------
N)
SAMPLE
Total Sample (No Filtration)
\/
Direct
Colorimetry
Hydrolysis
\/ Colorimetrv
Orthophosphate
Hydrolyzable §
Orthophosphate
Filter (through 0.45 y membrane filter)
\
Direct
Colorimetry
/ \
Dissolved
Orthophosphate
H2S04
Hydrolysis §
/ Colorimetry ^
Diss. Hydrolyzable
§ Orthophosphate
Persulfate
Digestion §
/ Colorimetry
Dissolved
Phosphorus
Persulfate
Digestion
\l/ Colorimetrv
Phosphorus
Figure 1. Analytical Scheme for Differentiation of Phosphorus Forms.
-------
(Phosphorus)
2.2 Only orthophosphate forms a blue color in this test. Polyphosphates
(and some organic phosphorus compounds) may be converted to the
orthophosphate form by manual sulfuric-acid-hydrolysis. Organic
phosphorus compounds may be converted to the orthophosphate form by
manual persulfate digestion . The developed color is measured
automatically on the AutoAnalyzer.
3. Definitions
3.1 The various forms of phosphorus are defined in Table 1.
4. Sample Handling and Preservation
4.1 If benthic deposits are present in the area being sampled, great care
should be taken not to include these deposits.
4.2 Sample containers may be of plastic material, such as cubitainers, or
of Pyrex glass.
4.3 If the analysis cannot be performed the same day of collection, the
sample should be preserved by the addition of 40 mg HgCl2 per liter
and refrigeration at 4°C. Note HgCl- interference under 5.4.
249
-------
TABLE I: PHOSPHORUS TERMINOLOGY (Phosphorus)
1. Phosphorus - all of tb_e phosphorus present in the sample regardless of
form, as measured by the persulfate digestion procedure. (00665)
_T
a. Orthophosphate (P-ortho)-inorganic phosphorus [PO.) ] in the sample
as measured by the direct colorimetric analysis procedure. (70507)
b. Hydrolyzable Phosphorus (P-hydro)-phosphorus in the sample as
measured by the sulfuric acid hydrolysis procedure, and minus pre-
determined orthophosphates. This hydrolyzable phosphorus includes
-4 -5
polyphosphates [(PJD-) , (P 0 ) , etc.] + some organic phosphorus. (00669)
c. Organic Phosphorus (P-org)-phosphorus (inorganic + oxidizible organic)
in the sample as measured by the persulfate digestion procedure, and
minus hydrolyzable phosphorus and orthophosphate. (00670)
2. Dissolved Phosphorus (P-D) - all of the phosphorus present in the filtrate
of a sample filtered through a phosphorus-free filter of 0.45 micron pore
size and measured by the persulfate digestion procedure. (00666)
a. Dissolved Orthophosphate (P-D, ortho) - as measured by the direct
colorimetric analysis procedure. (00671)
b. Dissolve Hydrolyzable Phosphorus (P-D, hydro) - as measured by the
sulfuric acid hydrolysis procedure and minus pre-determined dissolved
orthophosphates. (00672)
c. Dissolved Organic Phosphorus (P-D, org) - as measured by the persulfate
digestion procedure, and minus dissolved hydrolyzable phosphorus and
orthophosphate. (00673)
3. The following forms, when sufficient amounts of phosphorus are present in
the sample to warrant such consideration, may be calculated:
250
-------
(Phosphorus)
a. Insoluble Phosphorus (P-I) = (P) - (P-D). (00667)
(1) Insoluble orthophosphate (P-I, ortho) = (P, ortho) -
(P-D, ortho). (00674)
(2) Insoluble Hydrolyzable Phosphorus (P-I, hydro) =
(P, hydro) - (P-D, hydro). (00675)
(3) Insoluble Organic Phosphorus (P-l, org) = (P, org) -
(P-D, org). (00676)
4. All phosphorus forms shall be reported as P, mg/1, to the third place.
5. Interferences
5.1 It is reported^ ' that no interference is caused by copper, iron, or
silicate at concentrations many times greater than their greatest
reported concentration in sea water. However, high iron concentrations
can cause precipitation of phosphorus through the formation of clumps
in the bottom of the sample.
5.2 The salt error fox* samples ranging from 5 to 20 percent salt content
was found to be less than 1 percent^ •*.
5.3 Arsenate, in concentrations greater than found in sea water, does
not interfere '.
5.4 Mercury chloride, used as a preservative, interferes. This interference
is overcome by substituting a solution of sodium chloride (2.5 g/1) in
place of the distilled water (Line YY, 1.20 ml/min).
6. Apparatus
6.1 Technicon AutoAnalyzer consisting of:
6.1.1 Sampler I
6.1.2 Manifold
6.1.3 Proportioning Pump
251
-------
(Phosphorus)
6.1.4 Heating Bath, 50°C
6.1.5 Colorimeter equipped with 50 nan tubular flow cell and
650 nm filters
6.1.6 Recorder
6.2 Hot Plate or Autoclave
6.3 Acid-washed glassware: All glassware used in the determination
should be washed with hot 1:1 HC1 and rinsed with distilled water.
The acid-washed glassware should be filled with distilled water
and treated with all the reagents to remove the last traces of
phosphorus that might be adsorbed on the glassware. Preferably,
this glassware should be used only for the determination of phosphorus
and after use it should be rinsed with distilled water and kept
covered until needed again. If this is done, the treatment with
1:1 HC1 and reagents is only required occasionally. Commercial
detergents should never be used.
7. Reagents
7.1 Sulfuric acid solution, 5N: Dilute 70 ml of cone. H-SO. with distilled
water to 500 ml.
7.2 Potassium antimonyl tartrate solution: Weigh 0.3 g KCSbCOC.H.CL.l^
H-0, dissolve in 50 ml distilled water in 100 ml volumetric flask,
dilute to volume. Store at 4°C in a dark, glass-stoppered bottle.
7.3 Ammonium molybdate solution: Dissolve 4 g (NH.)6Mo_0_4.4H 0 in 100 ml
distilled water. Store in a plastic bottle at 4°C.
7.4 Ascorbic acid, 0.1M: Dissolve 1.8 g of ascorbic acid in 100 ml
of distilled water. The solution is stable for about a week if stored
at 4°C.
252
-------
(Phosphorus)
7.5 Combined reagent: Mix the above reagents in the following proportions
for 100 ml of the mixed reagent: 50 ml of 5N JUSO., 5 ml of potassium
antimonyl tartrate solution, 15 ml of ammonium molybdate solution, and
30 ml of ascorbic acid solution. MX after addition of each reagent.
All reagents must reach room temperature before they are mixed and
must be mixed in the order given. If turbidity forms in the combined
reagent, shake and let it stand for a few minutes until the turbidity
disappears before processing. This volume is sufficient for 4 hours
operation. Since the stability of this solution is limited, it must
be freshly prepared for each run.
7.6 Strong-acid solution: Slowly add 310 ml cone. H_SO. to 600 ml
distilled water. When cool, dilute to 1 liter.
7.7 Ammonium persulfate.
7.8 Wash water: Add 40 ml of strong acid solution (7.6) to 1 liter of
distilled water andjdilute to 2 liters. (Not to be used when only
orthophosphate is being determined).
7.9 Stock Solution: Dissolve 0.4393 g of pre-dried KH2P04 in distilled
water and dilute to 1 liter. 1 ml = 0.1 mg P.
7.10 Standard Solution A: Dilute 100 ml of stock solution to 1 liter.
1 ml = 0.01 mg P.
7.11 Standard Solution B: Dilute 100 ml of standard solution A to 1 liter.
1 ml = 0.001 mg P.
7.12 Prepare a series of standards by diluting suitable volumes of standard
solutions A and B to 100.0 ml with distilled water. The following
dilutions are suggested:
253
-------
(Phosphorus)
Cone.,
ml of Standard Solution B mg P/l
0.0 0.00
2.0 0.02
5.0 0.05
10.0 0.10
ml of Standard Solution A
2.0 0.20
5.0 0.50
8.0 0.80
10.0 1.00
Note: When the samples to be analyzed are saline waters, Substitute
Ocean Water (SOW) should be used for preparing the standards, other-
wise, distilled water is used. A tabulation of SOW composition
follows:
- 4.09g/l
- 0.20g/l
0.03g/l
•J «J *•
0.003g/l
8. Procedure
8.1 Phosphorus
8.1.1 Add 1 ml of strong-acid solution to a 50 ml sample in a 125-ml
Erlenmeyer flask.
8.1.2 Add 0.4 grams of ammonium persulfate.
8.1.3 Boil gently on a pre-heated hot plate for approximately
30-40 minutes or until a final volume of about 10 ml is reached.
Do not allow sample to go to dryness. Alternatively, heat for
30 minutes in an autoclave at 121°C (15-20 psi).
8.1.4 Cool and dilute the sample to 50.0 ml. If sample is not clear
at this point, filter.
254
NaCl
CaCl2 -
KBr
NaF
24.53g/l
1.16g/l
0.10g/l
0.003g/l
MgCl2 -
KC1
H3B03 -
5.20g/l
0.70g/l
0.03g/l
Na2S04
NaHC03
SrCl2
-------
(Phosphorus)
8.1.5 Determine phosphorus as outlined in 8.3 Orthophosphate.
8.2 Hydrolyzable Phosphorus
8.2.1 Add 1 ml of strong-acid solution to a 50 ml sample in a
125 ml Erlenmeyer flask.
8.2.2 Boil gently on a pre-heated hot plate for 30-40 minutes or
until a final volume of about 10 ml is reached. Do not
allow sample to go to dryness. Alternatively, heat for
30 minutes in an autoclave at 121°C (15-20 psi) .
8.2.3 Cool and dilute the sample to 50.0 ml. If sample is not
clear at this point, filter.
8.2.4 The sample is not ready for determination of phosphorus as
outlined in 8.3 Orthophosphate.
8.3 Orthophosphate
8.3.1 Set up manifold as shown in Figure 1.
8.3.2 Allow both colorimeter and recorder to warm up for 30 minutes.
Run a baseline with all reagents, feeding distilled water
through the sample line. Adjust dark current and operative
opening on colorimeter to obtain stable baseline.
8.3.3 Place wash water tubes (see 7.8) in Sampler, in sets of 2,
leaving every third position vacant. Set sample timing at 1.0
minutes.
8.3.4 Place standards in Sampler in order of decreasing concentration.
Complete filling of sampler tray with unknown samples.
8.4.5 Switch sample line from distilled water to Sampler and begin
analysis.
9. Calculation
9.1 Prepare standard curve by plotting peak heights of processed standards
against known concentrations. Compute concentrations of samples by
255
-------
(Phosphorus)
comparing sample peak heights with standard curve. Any sample whose
computed value is less than 5% of its immediate predecessor must be
rerun.
10. Precision and Accuracy
10.1 Six laboratories analyzed four natural water samples containing exact
increments of orthophosphate, with the following results:
Increment as
Orthophosphate
mg P/liter
0.04
0.04
0.29
0.30
Precision as
Standard Deviation
mg P/liter
0.019
0.014, ... .
0.087
0.066
Accuracy
Bias,
%
+ 16.7
- .8.3.:. .
-15.5
-12.8
as
Bias,
mg P/liter
+ .007
-.003
-.05
-.04
(FWQA Method Study 4, Automated Methods - In preparation).
10.2 In a single laboratory, using surface water samples at concentrations
of .04, 0.19, 0.35, and 0.84 mg P/l, standard deviations were ±0.005,
±0.000, ±0.003, and ±0.000, respectively (AQC Laboratory).
10.3 In a single laboratory, using surface water samples at concentrations
of 0.07 and 0.76 mg P/l, recoveries were 99% and 100%, respectively
(AQC Laboratory).
References
1. J. Murphy and J. Riley, "A Modified Single Solution Method for the
Determination of Phosphate in Natural Waters." Anal. Chim. Acta., 27,
31 (1962).
2. M. Gales, Jr., E. Julian, and R. Kroner, "Method for Quantitative Deter-
mination of Total Phosphorus in Water." Jour AWWA, 58y No. 10, 1363 (1966)
256
-------
N)
cn
LARGE MIXING COIL (LM)
QQQQOQQQ
HEATING BATH
SM
OQQQ
SM
0000
62
COLORIMETER
50mm TUBULAR f/c
650 nm FILTERS
•*•
WASTE
SAMPLER 1
.l/.l..
2.90 SAMPLE
0.80 AIR
1.20 ^DISTILLED WATER
0.42 MIXED REAGENT
PROPORTIONING PUMP
IX
RECORDER
SAMPLING TIME: 1.0 MIN.
WASH TUBES: TWO
FIGURE 1. PHOSPHORUS SINGLE REAGENT MANIFOLD
-------
PHOSPHORUS, ALL FORMS
(Automated Stannous Chloride Method)
STORE! NO:
, 0 , . SEE TABLE 1
1. Scope and Application
1.1 These methods cover the determination of specified forms of phosphorus
in surface waters, domestic and industrial wastes. They may be
applicable to sediment-type samples, sludges, algal blooms, etc., but
sufficient data is not available at this time to warrant such usage
when measurements for phosphorus content are required.
1.2 The methods are based on reactions that are specific for the ortho-
phosphate ion. Thus, depending on the prescribed pre-treatment of the
sample, the various forms of phosphorus given in Figure 1 may be
determined. These forms are, in turn, defined in Table 1.
1.2.1 Except for in-depth and detailed studies, the most commonly
measured forms are phosphorus and dissolved phosphorus, and
orthophosphate and dissolved orthophosphate. Hydrolyzable
phosphorus is normally found only in sewage-type samples 'and
insoluble forms of phosphorus, as noted, are determined by
calculation.
1.3 The methods are usable in the 0.01 to 1.0 mg P/l range.
Approximately 15 samples per hour can be analyzed.
2. Summary of Method
2.1 Phosphorus is determined by manually digesting the samples with ammonium
persulfate and sulfuric acid to convert the various forms of phosphorus
to the orthophosphate form and measurement of this orthophosphate on the
AutoAnalyzer.
2.2 In this colorimetric method, ammonium molybdate reacts with the ortho-
phosphate in an acid medium to form a heteropoly acid, molybdophosphoric
259
-------
to
ON
O
SAMPLE
Total Sample (No Filtration)
Direct
Colorimetry
H2S°4
Hydrolysis
Colorimetry
Orthophosphate
Hydrolyzable §
Orthophosphate
Filter (through 0.45p membrane filter)
\/
_v
Filtrate
\
Direct
Colorimetry
/
Dissolve
Orthophosphate
Ji
H2S04
Hydrolysis §
/ Colorimetry v
Diss. Hydrolyzable
§ Orthophosphate
Persulfate
Digestion 5
i Colorimetry
Dissolved
Phosphorus
Figure 1. Analytical Scheme for Differentiation of Phosphorus Forms
Persulfate
Digestion
\/ Colorimetry
Phosphorus
-------
(Phosphorus)
acid. This acid is reduced by stannous chloride to form the
intensely colored complex, molybdenum blue, which is directly
proportional to the amount of phosphorus.
3. Definitions
3.1 The various forms of phosphorus are defined in Table 1.
4. Sample Handling and Preservation
4.1 If benthic deposits are present in the area being sampled, great
care should be taken not to include these deposits.
4.2 Sample containers may be of plastic material, such as cubitainers,
or of Pyrex glass.
4.3 If the analysis cannot be performed the same day of collection, the
sample should be preserved by the addition of 40 mg HgCl2 per liter
and refrigeration at 4°C.
262
-------
(Phosphorus)
TABLE 1
PHOSPHORUS TERMINOLOGY
1. Phosphorus (P) - all of the phosphorus present in the sample regardless
of form, as measured by the persulfate digestion procedure. (00665)
a. Orthophosphate (P, ortho)-inorganic phosphorus [(PO.) ] in the
sample as measured by the direct colorimetric analysis procedure. (70507)
b. Hydrolyzable Phosphorus (P, hydro)-phosphorus in the sample as
measured by the sulfuric acid hydrolysis procedure, and minus pre-
determined orthophosphates. This hydrolyzable phosphorus includes
polyphosphates [(P_0_)~ , (P3°i{P~ ' etc-] + some organic phosphorus. (00669)
c. Organic Phosphorus (P,org)-phosphorus (inorganic + oxidizable
*
organic) in the sample as measured by the persulfate digestion procedure,
and minus hydrolyzable phosphorus and orthophosphate. (00670)
2. Dissolved Phosphorus (P-D) - all of the phosphorus present in the filtrate
of a sample filtered through a phosphorus-free filter of 0.45 micron pore
size and measured by the persulfate digestion procedure. (00666)
a. Dissolved Orthophosphate (P-D, ortho) - as measured by the direct
colorimetric analysis procedure. (00671)
b. Dissolved Hydrolyzable Phosphorus (P-D, hydro) - measured by the sulfuric
acid hydrolysis procedure and minus pre-determined dissolved
orthophosphates. (00672)
c. Dissolved Organic Phosphorus (P-D, org) - as measured by the persulfate
digestion procedure, and minus dissolved hydrolyzable phosphorus and
orthophosphate. (00673)
3. The following forms, when sufficient amounts of phosphorus are present in
the sample to warrant such consideration, may be calculated:
263
-------
(Phosphorus)
a. Insoluble Phosphorus = (?) - (P-D) • (00667)
(1) Insoluble orthophosphate (P-I, ortho) =. (P, ortho) - (P-D, ortho). (00674)
(2) Insoluble Hydrolyzable Phosphorus (P-I, hydro) = (P, hydro) -
(P-D, hydro). (00675)
(3) Insoluble Organic Phosphorus (P-I, org) = (P, org) - (P-D, org). (00676)
4. All phosphorus forms shall be reported as P, mg/1, to the third place.
5. Interferences
5.1 Method does not work on saline waters.
6. Apparatus
6.1 Acid-washed glassware: To prevent contamination, all glassware used
in the preparation of standards and actual determinations should be washed
with hot 1:1 HC1 and rinsed with distilled water. The acid-washed glass-
ware should be filled with distilled water and treated with all the reagents
to remove the last traces of phosphorus that might be adsorbed on the
glassware. Preferably, this glassware should be used only for the deter-
mination of phosphorus and after use it should be rinsed with distilled
water and kept covered until needed again. If this is done-, the treatment
with 1:1 HC1 and reagents is only required occasionally. Commercial
detergents should never be used.
6.2 Technicon AutoAnalyzer consisting of:
6.2.1 Sampler I.
6.2.2 Continuous Filter.
6.2.3 Manifold
6.2.4 Proportioning Pump.
6.2.5 Colorimeter equipped with 15 mm tubular flow cell and 650 nm
filters.
264
-------
(Phosphorus)
6.2.6 Recorder.
6.3 Hot Plate or Autoclave
7. Reagents
7.1 Sulfuric acid solution: Cautiously add 310 ml of concentrated
sulfuric acid slowly and with stirring to about 600 ml of distilled
water. Cool and dilute to 1 liter.
7.2 Ammonium molybdate solution: Dissolve 12.5 g of (NH.)fiMo_CL. .4H_0 in
175 ml of distilled water. Cautiously add 77.5 ml of concentrated
sulfuric acid slowly and with stirring to 400 ml of distilled water.
Cool. Add the molybdate solution to the acid solution and dilute to
1 liter.
7.3 Stannous chloride solution: Dissolve 2.5 g of fresh SnCl_.2H?0 in
20 ml of hydrochloric acid. Warming on a hot plate will aid in dissolving
this material. Dilute to 400 ml. Stable for 1 week at room temperature;
one month at 4°C.
7.4 Wash water: Add 40 ml of sulfuric acid solution (Reagent 7.1) to
1 liter of distilled water and dilute to 2 liters.
7.5 Stock Solution: Dissolve 0.4393 g of pre-dried KH2P04 *n distilled
water and dilute to 1 liter. 1 ml = 0.1 mg P.
7.6 Standard Solution A: Dilute 100 ml of stock solution to 1 liter.
1 ml = 0.01 mg P.
7.7 Standard Solution B: Dilute 100 ml of standard solution A to 1 liter.
1 ml = 0.001 mg P.
7.8 Prepare a series of standards by diluting suitable volumes of standard
solutions A and B to 100.0 ml with distilled water. The following
dilutions are suggested:
265
-------
(Phosphorus)
Cone.,
ml of Standard Solution B mg P/l
1.0 0.01
2.0 0.02
5.0 0.05
10.0 • 0.10
ml of Standard Solution A
2.0 0.20
5.0 0.50
8.0 0.80
10.0 1.00
7.9 Ammonium persulfate, reagent grade.
7.10 NaOH-EDTA Solution: Dissolve 65 g NaOH and 6 g EDTA in distilled
water and dilute to 1 liter.
8. Procedure
8.1 Phosphorus
8.1.1 Add 1 ml of sulfuric acid solution to a 50-ml sample in a
125-ml Erlenmeyer flask.
!
8.1.2 Add 0.4 g ammonium persulfate.
8.1.3 Boil gently on a pre-heated hot plate for approximately 30-40
minutes or until a final volume of about 10 ml is reached. Do
not allow sample to go to dryness. Alternatively, heat for 30
minutes in an autoclave at 121°C (15-20 psi) .
8.1.4 Cool and dilute the sample to 50.0 ml. If sample is not clear
at this point, filter.
8.1.5 The sample is now ready for automatic analysis as outlined in
8.3 Orthophosphate.
8.2 Hydrolyzable Phosphorus
8.2.1 Add 1 ml of sulfuric acid solution to a 50-ml sample in a
125-ml Erlenmeyer flask.
266
-------
(Phosphorus)
8.2.2 Boil gently on a pre-heated hot plate for approximately
30-40 minutes or until a final volume of about 10 ml is
reached. Do not allow sample to go to dryness. Alter-
natively, heat for 30 minutes in an autoclave at 121°C (15-20
psi).
8.2.3 Cool and dilute the sample to 50.0 ml. If sample is not clear
at this point, filter.
8.2.4 The sample is now ready for automatic analysis as outlined
in 8.3 Orthophosphate.
8.3 Orthophosphate
8.3.1 Set up manifold as shown in Figure 1.
8.3.2 Allow both colorimeter and recorder to warm up for 30 minutes.
Run a baseline with all reagents, feeding distilled water
through the sample line. Adjust dark current and operative
opening on colorimeter to obtain stable baseline.
8.3.3 Place wash water tubes (see 7.4) in alternate openings in
Sampler and set sample timing at 2.0 minutes. Use distilled
water, instead of acid-wash water when only Orthophosphate
is being determined.
8.3.4 Place standards in Sampler in order of decreasing concentration.
Complete filling of sampler tray with unknown samples.
8.3.5 Switch sample line from distilled water to Sampler and begin
analysis.
8.3.6 At end of run, clean out manifold system with NaOH-EDTA solution.
9. Calculations
9.1 Prepare standard curve by plotting peak heights of processed standards
against known concentrations. Compute concentration of samples by
comparing sample peak heights with standard curve.
267
-------
(Phosphorus)
10. Precision and Accuracy
10.1 In a single laboratory, using surface water samples at concen-
trations of 0.06, 0.11, 0.48, and 0.62 mg P/l, the standard deviation
was ±0.004 (AQC Laboratory).
10.2 In a single laboratory, using surface water samples at concen-
trations of 0.11 and 0.74 mg P/l, recoveries were 90% and 95%,
respectively (AQC Laboratory).
References
1. Standard Methods for the Examination of Water and Wastewater, 12th Edition,
p. 234, Amer. Pub. Health Assoc., Inc., New York, N.Y. (1965).
2. M. Gales, Jr., E. Julian, and R. Kroner, "Method for Quantitative Determination
of Total Phosphorus in Water." Jour. AWWA, 58, No. 10, 1363 (1966).
268
-------
DOUBLE
DELAY
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i,
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(LM)
opooj
V
J
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>
;
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^
IU 1CTC ^^
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P B
Y Y
P P
P P
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^2.90
Xo^o^s. >
(I ° |)*«WH
\OOOx
AMMONIUM n
^'•20 MOLYBDATE /Ou5_
^2.50 SAMI
2.50
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CONTINUOUS F
0.23 STANNOUS CHLORIDE
^2.50 WASTE
PROPORTIONING PUMP
. , , ^
IX
SAMPLING TIME • 2 MIN.
WASH TUBES • ONE
COLORIMETER RECORDER
15mm TUBULAR f/c
650 " m FILTERS
FIGURE 1 • PHOSPHORUS MANIFOLD
-------
SELENIUM
(Diaminobenzidine Method)
STORE! NUMBERS:
DISSOLVED 01145
TOTAL 01147
1. Scope and Application
1.1 This colorimetric method covers the determination of selenium in
drinking waters and surface waters, domestic and industrial
wastes, and saline waters.
1.2 The method covers the range from 0.003 - 0.05 mg selenium per
liter.
2. Summary of Method
2.1 All selenium compounds present in the sample are first oxidized to
selenate by acid permanganate. The selenate is then reduced to
selenite. Addition of diaminobenzidine reagent forms the piaz-
selenol complex which is subsequently extracted into toluene and
the absorbance measured at 420 nm. The piazselenol color is
stable, but evaporation of toluene concentrates the color to a
marked degree in a few hours.
3. Comments
3.1 For the measurement of dissolved selenium, the sample must first
be filtered through a 0.45 y membrane filter.
3.2 Evaporation of solutions of sodium selenate to complete dryness can
result in substantial loss of selenium unless calcium has been added
to the sample.
3.3 Temperature, time, and acid concentrations are critical to obtain
quantitative reduction without loss of selenium. The optimum pH
for the formation of piazselenol is approximately 1.5.
271
-------
(Selenium)
3.4 No inorganic compounds are known to give a positive interference.
Negative interference results from compounds that lower the con-
centration of diaminobenzidine by oxidizing this reagent. The
addition of EDTA eliminates negative interference from at least
2.5 mg ferric iron. Iodine, and to a lesser extent bromide, causes
low results.
3.5 When iodide or bromide interferences are encountered, a distillation
step is required. This entails the addition of 50 ml KBr-FLSO.
reagent and 1 ml 30% H?0_ to the residue remaining after the
evaporation step. The mixture is distilled until the color of
bromine is gone from the flask. Diaminobenzidine is then added
to the distillate and the piazselenol complex extracted into toluene.
4. Precision and Accuracy
4.1 A synthetic unknown sample containing 20 Mg/1 Se, 40 yg/1 As,
250 yg/1 Be, 240 yg/1 B, and 6 yg/1 V in distilled water was
determined by the diaminobenzidine method, with a relative standard
deviation of 21.2% and a relative error of 5.0% in 35 laboratories.
5. Reference
5.1 The procedure to be used for this determination is found in:
Standard Methods for the Examination of Water and Wastewater,
13th Edition, p 296 Method 150 A (1971).
272
-------
SILICA, DISSOLVED
STORE! NUMBER: 00955
1. Scope and Application -
1.1 This method is applicable to drinking waters and surface waters,
domestic and industrial wastes, and saline waters.
1.2 Working range of method is approximately 2 to 25 mg silica/1.
The upper range can be extended by taking suitable aliquots;
the lower range can be extended by the addition of amino-naphthol-
sulfonic acid solution, as described in ASTM reference.
2. Summary of Method
2.1 A well-mixed sample is filtered through a 0.45 y membrane filter.
The filtrate, upon the addition of molybdate ion in acidic
solution, forms a greenish-yellow color complex proportional to
the dissolved silica in the sample. The color complex is then
measured spectrophotometrically.
3. Comments
3.1 Excessive color and/or turbidity interfere. Correct by running
blanks prepared without addition of the ammonium molybdate solution.
4. Precision and Accuracy
4.1 Photometric evaluations by the amino-naphthol-sulfonic acid pro-
cedure have an estimated precision of ±0.10 mg/1 in the range from
0 to 2 mg/1 (ASTM).
4.2 Photometric evaluation of the silico-molybdate color in the range
from 2 to 50 mg/1 have an estimated precision of approximately 4
percent of the quantity of silica measured (ASTM).
273
-------
(Silica, Dissolved)
5. Reference
5.1 The procedure to be used for this determination is found in:
Standard Methods for the Examination of Water and Wastewater,
13th Edition, p. 303, Method 151B U971).
ASTM Standards, Part 23, Water; Atmospheric Analysis, p. 91,
Method D859-68 (1970).
274
-------
SOLIDS, FILTERABLE (DISSOLVED)
STORET NO. 70500
1. Scope and Application ~~
1.1 This method is applicable to surface waters, domestic and industrial
wastes, and saline waters.
1.2 The practical range of the determination is 10 mg/1 to 20,000 mg/1.
2. Summary of Method
2.1 A well-mixed sample is filtered through a standard glass fiber filter.
The filtrate is evaporated and dried to constant weight at 180°C.
3. Definitions
3.1 Filterable solids are defined as those solids capable of passing
through a standard glass fiber filter and dried to constant weight
at 180°C.
4. Sample Handling and Preservation
4.1 Samples should be analyzed as soon as practicable.
5. Interferences
5.1 Highly mineralized waters containing significant concentrations of
calcium, magnesium, chloride and/or sulfate may be hygroscopic and will
require prolonged drying and desiccation and quick weighing.
5.2 Samples containing high concentrations of bicarbonate will require
careful and possibly prolonged drying at 180°C to insure that all the
bicarbonate is converted to carbonate.
5.3 Too much residue in the evaporating dish will crust over and entrap
water that will not be driven off during drying. Total residue should
be limited to about 200 mg.
6. Apparatus
6.1 Glass fiber filter discs, 4.7 cm or 2.2 cm, without organic binder,
275
-------
(Solids, Filterable - Dissolved)
Reeve Angel type 984 H, Gelman type A, or equivalent.
6.2 Filter holder, membrane filter funnel or Gooch crucible adapter.
6.3 Suction flask, 500 ml.
6.4 Gooch crucibles, 25 ml (if 2.2 cm filter is used).
6.5 Evaporating dishes, porcelain, 100 ml volume. (Vycor or platinum
dishes may be substituted).
6.6 Steam bath.
6.7 Drying oven, 180°C±2°C.
6.8 Desiccator.
6.9 Analytical balance, 200 g capacity, capable of weighing to 0.1 mg.
7. Procedure
7.1 Preparation of glass fiber filter disc: Place the disc on the membrane
filter apparatus or insert into bottom of a suitable Gooch crucible.
While vacuum is applied, wash the disc with three successive 20 ml
volumes of distilled water. Remove all traces of water by continuing
to apply vacuum after water has passed through. Remove filter from
membrane filter apparatus or both crucible and filter if Gooch crucible
is used, and dry in an oven at 103-105°C for one hour. Remove to
desiccator and store until needed.
7.2 Preparation of evaporating dishes: Heat the clean dish to 550°C for
one hour in a muffle furnace. Cool in desiccator and store until needed.
Weigh immediately before use.
7.3 Assemble the filtering apparatus and begin suction. Shake the sample
vigorously and rapidly transfer 100 ml to the funnel by means of a 100
ml volumetric cylinder. If suspended matter is low, a larger volume
may be filtered.
276
-------
(Solids, Filterable - Dissolved)
7.4 Filter the sample through the glass fiber filter and continue to
apply vacuum for about 3 minutes after filtration is complete to
remove as much water as possible.
7.5 Transfer 100 ml (or a larger volume) of the filtrate to a weighed
evaporating dish and evaporate to dryness on a steam bath.
7.6 Dry the evaporated sample for at least one hour at 180±2°C. Cool
in a desiccator and weigh. Repeat the drying cycle until a constant
weight is obtained or until weight loss is less than 0.5 mg.
7.7 Note: The filtrate from the test for SOLIDS, NON-FILTERABLE, may be
used for this determination.
8. Calculation :
i
8.1 Calculate filterable solids as follows:
_.,„ ,. , ,, (Wt. of dried residue + dish) -fwt. of dish) x 1000
Flit. SOlldS, mg/1 = V rr-^ -. , ./ ^ 1
' 6 Volume of filtrate used
9. Precision and Accuracy
9.1 Precision data are not available at this time.
9.2 Accuracy data on actual sample cannot be obtained.
277
-------
SOLIDS, NON-FILTERABLE (SUSPENDED)
1. Scope and Application STORET NO. 00550
1.1 This method is applicable to surface waters, domestic and industrial
wastes, and saline waters.
1.2 The practical range of the determination is 20 mg/1 to 20,000 mg/1.
2. Summary of Method
2.1 A well-mixed sample is filtered through a standard glass fiber filter,
and the residue retained on the filter is dried to constant weight at
103-105°C.
3. Definitions
3.1 Non-filterable solids are defined as those solids which are retained by
a standard glass fiber filter and dried to constant weight at 103-105°C.
4. Sample Handling and Preservation
4.1 Non-homogenous particulates such as leaves, sticks, fish, and lumps of
fecal matter should be excluded from the sample.
4.2 Preservation of the sample is not practical; analysis should begin as
soon as possible.
5. Interferences
5.1 Too much residue on the filter will entrap water and may require
prolonged drying.
6. Apparatus
6.1 Glass fiber filter discs, 4.7 cm or 2.2 cm, without organic binder,
Reeve Angel type 934-H or 984-H, Gelman type A, or equivalent.
6.2 Filter holder, membrane filter funnel or Gooch crucible adapter.
6.3 Suction flask, 500 ml.
6.4 Gooch crucibles, 25 ml (if 2.2 cm filter is used).
278
-------
(Solids, Non-Filterable - Suspended)
6.5 Drying oven, 103-105°C.
6.6 Desiccator.
6.7 Analytical balance, 200 g capacity, capable of weighing to 0.1 mg.
7. Procedure
7.1 Preparation of glass fiber filter disc: Place the disc on the
membrane filter apparatus or insert into bottom of a suitable Gooch
crucible. While vacuum is applied, wash the disc with three
successive 20 ml volumes of distilled water. Remove all traces of
water by continuing to apply vacuum after water has passed through.
Remove filter from membrane filter apparatus or both crucible and
filter if Gooch crucible is used, and dry in an oven at 103-105°C for
\
one hour. Remove to desiccator and store until needed. Weigh
immediately before use.
7.2 Assemble the filtering apparatus and begin suction. Shake the sample
vigorously and rapidly transfer 100 ml to the funnel by means of a
100 ml volumetric cylinder. If suspended matter is low, a larger
volume may be filtered.
7.3 Carefully remove the filter from the membrane filter funnel assembly.
Alternatively, remove crucible and filter from crucible adapter. Place
in drying oven and dry at 103-105°C to constant weight.
8. Calculations
8.1 Calculate non-filterable solids as follows:
... ,. (Wt. of filter + residue)-Cwt. of filter) x 1000
Non-filterable solids, mg/1 = ml of sample filtered
9. Precision and Accuracy
9.1 Precision data are not available at this time.
9.2 Accuracy data on actual samples cannot be obtained.
279
-------
1. Scope and Application
SOLIDS, TOTAL
STORET NO. 00500
1.1 This method is applicable to surface waters, domestic and industrial
wastes, and saline waters.
1.2 The practical range of the determination is from 10 mg/1 to 30,000 mg/1.
2. Summary of Method
2.1 A well mixed aliquot of the test sample is quantitatively transferred
to a pre-weighed evaporating dish and evaporated to dryness at 103-105°C.
3. Definitions
3.1 Total Solids are defined as the sum of the homogenous suspended and
dissolved materials in a sample.
4. Sample Handling and Preservation
4.1 Samples should be analyzed as soon as practicable.
5. Interferences
5.1 Large, floating particles or submerged agglomerates (non-homogenous
materials) should be excluded from the test sample.
5.2 Floating oil and grease, if present, should be included in the sample
and dispersed by a blender device before aliquoting.
6. Apparatus
6.1 Evaporating dishes, porcelain, 90 mm, 100-ml capacity. (Vycor or
platinum dishes may be substituted and smaller size dishes may be
used if required.)
7. Procedure
7.1 Heat the clean evaporating dish to 550±50°C for 1 hour in a muffle
furnace. Cool, desiccate, weigh and store in desiccator until ready
for use.
280
-------
(Solids, Total)
7.2 Transfer a measured aliquot of sample to the pre-weighed dish and
evaporate to dryness on a steam bath or in a drying oven.
7.2.1 Choose an aliquot of sample sufficient to contain a residue
of at least 25 mg. To obtain a weighable residue, successive
aliquots of sample may be added to the same dish.
7.2.2 If the evaporation is performed in a drying oven, the temperature
should be lowered to approximately 98°C to prevent boiling and
splattering of the sample.
7.3 Dry the evaporated sample for at least 1 hour at 103-105°C. Cool in a
desiccator and weigh. Repeat the cycle of drying at 103-105°C, cooling,
desiccating and weighing until a constant weight is obtained or until
loss of weight is less than 4% of the previous weight, or 0.5 mg,
whichever is less.
8. Calculation
8.1 Calculate total solids as follows:
-, c i-j /i (Wt- of sample + dishl-(wt. of dish) 1000
Total Solids, mg/1 =l P Vol. of Sample
9. Precision and Accuracy
9.1 Precision and accuracy data are not available at this time.
281
-------
SOLIDS, VOLATILE
STORE! No: Total 00505
Suspended 00515
Dissolved 00520
1. Scope and Application
1.1 This method determines the weight of solid material combustible at
550°C.
1.2 The test is useful in obtaining a rough approximation of the amount
of organic matter present in the solid fraction of sewage, activated
sludge, industrial wastes, or bottom sediments.
2. Summary of Method
2.1 The residue obtained from the determination of total, suspended, or
dissolved solids is ignited at 550°C in a muffle furnace. The loss
of weight on ignition is reported as mg/1 volatile solids.
3. Comments
3.1 The test is subject to many errors due to loss of water of crystalliza-
tion, loss of volatile organic matter prior to combustion, incomplete
oxidation of certain complex organics, and decomposition of mineral
salts during combustion.
3.2 The results should not be considered an accurate measure of organic
carbon in the sample, but maybe useful in the control of plant
operations.
3.3 The principal source of error in the determination is failure to obtain
a representative sample,
4. Precision and Accuracy
A collaborative study involving three laboratories examining four
samples by means of ten replicates showed a standard deviation of
±11 mg/1 at 170 mg/1 volatile solids concentration. (Reference)
282
-------
(Solids, Volatile)
5. Reference
The procedure to be used for this determination is found in:
Standard Methods for the Examination of Water and Wastewater, 13th
Edition, P. 538, Method 224D (1971).
283
-------
SPECIFIC CONDUCTANCE
STORET NUMBER: 00095
1. Scope and Application
1.1 This method is applicable to drinking waters and surface waters,
domestic and industrial wastes, and saline waters.
2. Summary of Method
2.1 The specific conductance of a sample is measured by use of a self-
contained conductivity meter, Wheatstone bridge-type, or equivalent.
2.2 Samples are preferably analyzed at 25°C. If not, temperature cor-
rections are made and results reported at 25°C.
3. Comments
3.1 Instrument must be standardized with KC1 solution before daily use.
3.2 Conductivity cell must be kept clean.
3.3 Field measurements with comparable instruments are reliable.
4. Precision and Accuracy
4.1 Forty-one analysts in 17 laboratories analyzed six synthetic water
samples containing increments of inorganic salts, with the following
results:
Increment as
Specific Conductance
ymhos/cm
100
106
808
848
1640
1710
Precision as
Standard Deviation
ymhos/cm
7.55
8.14
66.1
79.6
106
119
Accuracy as
Bias,
%
-2.02
-0.76
-3.63
-4.54
-5.36
-5.08
Bias,
ymhos/cm
-2.0
-0.8
-29.3
-38.5
-87.9
-86.9
(FWPCA Method Study 1, Mineral and Physical Analyses).
284
-------
(Specific Conductance)
4.2 In a single laboratory (AQC), using surface water samples with an
average conductivity of 536 ymhos/cm @ 25°C, the standard deviation
was ±6.
5. References
5.1 The procedure to be used for this determination is found in:
Standard Methods for the Examination of Water and Wastewater, 13th
Edition, p. 323, Method 154 (1971).
ASTM Standards, Part 23, Water; Atmospheric Analysis, p. 179,
Method D1125-64 (1970).
285
-------
SULFATE
STORET NUMBER: 00945
1. Scope and Application
1.1 This method is applicable to drinking waters and surface waters,
domestic and industrial wastes.
1.2 The method is suitable for all concentration ranges of sulfate;
however, in order to obtain reliable readings, use a sample aliquot
containing not more than 40 mg SO./I.
2. Summary of Method
2.1 Sulfate ion is converted to a barium sulfate suspension under
controlled conditions. The resulting turbidity is determined by
a photoelectric colorimeter or spectrophotometer and compared to
a curve prepared from standard sulfate solutions.
2.2 Suspended matter and color interfere. Correct by running blanks
from which the barium chloride has been omitted.
3. Comments
3.1 Proprietary reagents, such as Hach SULFAVER or equivalent, are
acceptable.
4. Precision and Accuracy
4.1 Thirty-four analysts in 16 laboratories analyzed six synthetic
water samples containing exact increments of inorganic sulfate,
with the following results:
Increment as
Sulfate
mg/liter
8.6
9.2
110
122
188
199
Precision as
Standard Deviation
mg/liter
2.30
1.78
7.86
7.50
9.58
11.8
Accuracy as
Bias,
%
-3.72
-8.26
-3.01
-3.37
+0.04
-1.70
Bias,
mg/liter
-.3
-.8
-3.3
-4.1
+ .1
-3.4
(FWPCA Method Study 1, Mineral and Physical Analyses).
286
-------
(Sulfate)
5. Reference
5.1 The procedure to be used for this determination is found in:
Standard Methods for the Examination of Water and Wastewater,
13th Edition, p. 334, Method 156C (1971).
ASTM Standards, Part 23, Water; Atmospheric Analysis, p. 54,
Method D516-68 (1970).
287
-------
SULFATE
(Automated Chloranilate Method)
1. Scope and Application STORE! NO. 00945
1.1 This automated method is applicable to surface waters, domestic and
industrial wastes, and saline waters, in the range of 10 to 400 mg
SO./I. Approximately 15 samples per hour can be analyzed.
2. Summary of Method
2.1 When solid barium chloranilate is added to a solution containing
sulfate, barium sulfate is precipitated, releasing the highly colored
acid chloranilate ion. The color intensity in the resulting chloranilic
acid is proportional to the amount of sulfate present.
3. Sample Handling and Preservation
3.1 No special requirements.
4. Interferences
4.1 Cations, such as calcium, aluminum, and iron, interfere by precipitating
the chloranilate. These ions are removed automatically by passage
through an ion exchange column.
5. Apparatus
5.1 Technicon AutoAnalyzer consisting of:
5.1.1 Sampler I.
5.1.2 Continuous filter.
5.1.3 Manifold.
5.1.4 Proportioning pump.
5.1.5 Colorimeter equipped with 15 mm tubular flow cell and 520 nm
filters.
5.1.6 Recorder.
288
-------
(Sulfate)
5.1.7 Heating bath, 45°C.
5.2 Magnetic stirrer.
6. Reagents
6.1 Barium chloranilate: Add 9 g of barium chloranilate (BaC-C^O.)
to 333 ml of ethyl alcohol and dilute to 1 liter with distilled
water.
6.2 Acetate buffer, pH 4.63: Dissolve 13.6 g of sodium acetate in
distilled water. Add 6.4 ml of acetic acid and dilute to 1 liter with
distilled water. Make fresh weekly.
6.3 NaOH-EDTA Solution: Dissolve 65 g of NaOH and 6 g of EDTA in distilled
water and dilute to 1 liter.
Note: This solution is also used to clean out manifold system at end
of sampling run.
6.4 Ion Exchange Resin: Dowex-50 W-X8, ionic form -H .
Note: Column is prepared by sucking a slurry of the resin into 12
inches of 3/16-inch OD sleeving. This may be conveniently done by
using a pipette and a loose-fitting glass wool plug in the sleeve.
The column, upon exhaustion, turns red.
6.5 Stock solution: Dissolve 1.4790 g of pre-dried Na-SO in distilled
water and dilute to 1 liter. 1 ml = 1 mg.
6.5.1 Prepare a series of standards by diluting suitable volumes of
stock solution to 100.0 ml with distilled water. The following
dilutions are suggested:
289
-------
(Sulfate)
ml of Stock Solution Cone., mg/1
1.0 10
2.0 20
4.0 40
6.0 60
8.0 80
10.0 100
15.0 150
20.0 200
30.0 300
40.0 400
7. Procedure
7.1 Set up manifold as shown in Figure 1. (Note that any precipitated
BaSO. and the unused barium chloranilate are removed by filtration.
If any BaSO. should come through the filter, it is complexed by the
NaOH-EDTA reagent).
7.2 Allow both colorimeter and recorder to warm up for 30 minutes. Run
a baseline with all reagents, feeding distilled water through the
sample line. Adjust dark current and operative opening on colorimeter
to obtain suitable baseline.
7.3 Place distilled water wash tubes in alternate openings in sampler and
set sample timing at 2.0 minutes.
7.4 Place working standards in sampler in order of decreasing concentration.
Complete filling of sampler tray with unknown samples.
7.5 Switch sample line from distilled water to sampler and begin analysis.
8. Calculation
8.1 Prepare standard curve by plotting peak heights of processed standards
against known concentrations. . Compute concentration of samples by
comparing sample peak heights with standard curve.
9. Precision and Accuracy
9.1 In a single laboratory (AQC), using surface water samples at concentra-
tions of 39, 111, 188, and 294 mg SO./I, the standard deviations were
290
-------
(Sulfate)
±0.6, ±1.0, ±2.2, and ±0.8, respectively.
9.2 In a single laboratory (AQC) using surface water samples at concen-
trations of 82 and 295 mg SO./I, recoveries were 99% and 102%,
respectively.
Reference
1. R.J. Bertolocini and J.E. Barney, Anal. Chem., 29, 283 (1957).
2. M.E. Gales, Jr., W.H. Kaylor and J.E. Longbottom, "Determination of
Sulphate by Automatic Colorimetric Analysis." Analyst, 95, 97 (1968).
291
-------
LM
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to
to
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1 EXCHANGE
1
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0 < W
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P tf P
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SMALL
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COIL
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COLORIMETER
15mm TUBULAR f/c
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CHLORANILATE
BLUE BLUE 1.60 AIR
R 0.80 BUFFER
JJJ EDTA-NaOH
CONTINUOUS FILTER
WASTE
0 3.40
< P 2.50
PROPORTIONING PUMP
SAMPLE
WASTE
t
•
V
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SAMPLING TIME • 2 MIN.
WASH TUBES • ONE
RECORDER
FIGURE 1 - SULFATE MANIFOLD
-------
SULFIDE
Titrimetric (Iodine) Method
STORET NO.
Total: 00745
Dissolved: 00746
1. Scope and Application
1.1 This method is applicable to the measurement of total and dissolved
sulfides in drinking waters, surface waters, domestic and industrial
wastes, and saline waters.
1.2 Acid insoluble sulfides are not measured by the use of this test.
(Copper sulfide is the only common sulfide in this class).
1.3 This method is suitable for the measurement of sulfide in concen-
trations above 1 mg/1.
2. Summary of Method
2.1 Sulfides are stripped from the acidified sample with an inert gas and
collected in a zinc acetate solution. Excess iodine added to the
zinc sulfide suspension reacts with the sulfide under acidic conditions.
Thiosulfate is used to measure unreacted iodine to indicate the
quantity of iodine consumed by sulfide.
3. Comments
3.1 Reduced sulfur compounds, such as sulfite, thiosulfate and hydrosulfite,
which decompose in acid may yield erratic results. Also, volatile
iodine-consuming substances will give high results.
3.2 Samples must be taken with a minimum of aeration. Sulfide
may be volatilized by aeration and any oxygen inadvertently added
to the sample may convert the sulfide to an unmeasurable form.
3.3 If the sample is not preserved with zinc acetate, the analysis must
be started immediately. Similarly, the measurement of dissolved
sulfides must also be commenced immediately.
294
-------
(Sulfide)
4. Precision and Accuracy
4.1 Precision and accuracy for this method have not been determined,
but it is claimed that the iodimetric titration of the zinc
sulfide is quite accurate.
5. References
5.1 The procedure to be used for this determination is found in:
Standard Methods for the Examination of Water and Wastewaters,
13th Edition, pp 551-555, Method No. 228A (1971).
295
-------
TEMPERATURE
STORET Number: 00010
1. Scope and Application
1.1 This method is applicable to drinking waters and surface waters,
domestic and industrial wastes, and saline waters.
2. Summary of Method
2.1 Temperature measurements may be made with any good grade of
mercury-filled or dial type centigrade thermometer, or a
thermistor.
3. Comments
3.1 Measurement device should be checked against a precision
thermometer certified by the National Bureau of Standards.
I
4. Precision and Accuracy,
i
4.1 There is no acceptable procedure for determining the precision
and accuracy of this test.
5. Reference
5.1 The procedure to be used for this determination is found in:
Standard Methods for the Examination of Water and Wastewater,
13th Edition, p. 348, Method 162 (1971).
296
-------
THRESHOLD ODOR STORET NO-
(Consistent Series Method) 60°C: 00086
ROOM TEMP: 00085
1. Scope and Application
1.1 This method is applicable to the determination of threshold odor of
finished waters, surface waters, domestic and industrial wastes, and
saline waters.
1.2 Highly odorous samples are reduced in concentration proportionately
before being tested. Thus, the method is applicable to samples
ranging from nearly odorless natural waters to industrial wastes with
threshold odor numbers in the thousands.
2. Summary of Method '
2.1 The sample of water is diluted with odor-free water until a dilution
that is of the least definitely perceptible odor to each tester is
found. The resulting ratio by which the sample has been diluted is
called the "threshold odor number" (T.O.).
2.2 People vary widely as to odor sensitivity, and even the same person
will not be consistent in the concentrations he can detect from day to
day. Therefore, panels of not less than five persons, and preferably
10 or more, are recommended to overcome the variability of using one
observer.^ '
2.2.1 As an absolute minimum, two persons are necessary: One to make
the sample dilutions and one to determine the threshold odor.
3. Sample Handling and Preservation
3.1 Water samples must be collected in glass bottles with glass or Teflon-
lined closures.
297
-------
(Threshold Odor)
3.1.1 Plastic containers are not reliable for odor samples and must
not be used.
3.2 Odor tests should be eompleted as soon as possible after collection
of the sample. If storage is necessary, collect at least 1000 ml of
sample in a bottle filled to the top. Refrigerate, making sure no
extraneous odors can be drawn into the sample as the water cools.
4. Interferences
4.1 Most tap waters and some waste waters are chlorinated. It is often
desirable to determine the odor of the chlorinated sample as well as
of the same sample after removal of chlorine. Dechlorination is
achieved using sodium thiosulfate in exact stoichiometric quantity.
j
4.1.1 It is important to check a blank to which a similar amount of
dechlorinating agent has been added to determine if any odor
has been imparted. Such odor usually disappears upon standing
if excess reagent has not been added.
5. Apparatus
5.1 Odor-free glassware: Glassware must be freshly cleaned shortly before
use, with non-odorous soap and acid cleaning solution followed by
rinsing with odor-free water. Glassware used in odor testing should
be reserved for that purpose only. Rubber, cork, and plastic stoppers
must not be used.
5.2 Constant temperature bath: A water bath or electric hotplate capable
of maintaining a temperature control of ±1°C for performing the odor
test at 60°C. The temperature bath must not contribute any odor to
the odor flasks.
5.3 Odor Flasks: Glass stoppered 500 ml (ST 32) Erlenmeyer flasks, or
298
-------
(Threshold Odor)
wide-mouthed 500 ml Erlenmeyer Flasks equipped with Petri dishes as
cover plates.
NOTE: Narrow-mouth vessels are not suitable for running odor tests.
Potential positive bias due to color and/or turbidity of water
sample under observation can be eliminated by wrapping odor
flasks in aluminum foil, painting flasks with non-odorous
paint, or by using red actinic Erlenmeyer flasks.
5.4 Sample Bottles: Glass bottles with glass or Teflon-lined closures.
5.5 Pipets, measuring: 10.0 and 1.0 ml graduated in tenths.
5.6 Graduate cylinders: 250, 200, 100, 50, and 25 ml.
5.7 Thermometer: 0-110°C (±1°C), chemical or metal stem dial type.
5.8 Odor free water generator: See Figure 1.
6. Reagents
6.1 Odor-free water: Odor-free dilution water must be prepared as needed
by filtration through a bed of activated carbon. Most tap waters are
suitable for preparation of odor-free waters, except that it is
necessary to check the filtered water for chlorine residual, unusual
salt concentrations, or unusually high or low pH. All these may
affect some odorous samples.
Where supplies are adequate, distilled water avoids these problems
as a source of odor-free water. A convenient odor-free water generator
may be made as shown in Figure 1. Pass tap or distilled water through
the odor-free water generator at a rate of 0.1 liter/minute. When the
generator is first started, it should be flushed to remove carbon fines
f31
before the odor-free water is used. The carbon cartridge, ' or a
comparable assembly, is also suitable.
299
-------
2 HOLE
RUBBER STOPPER
GRANULAR
4xlO-MESH
ACTIVATED
CARBON
I in.
PEA SIZE
GRAVEL
Fig. 1. Odor-free water generator
300
-------
(Threshold Odor)
6.1.1 The quality of water obtained from the odor-free water
generator should be checked daily at the temperature tests
are to be conducted (room temperature and/or 60°C). The life
of the carbon will vary with the condition and amount of water
filtered. Subtle odors of biological origin are often found
if moist carbon filters are permitted to stand idle between
test periods. Detection of odor in the water coming through
the carbon indicates a change of carbon is needed.
7. Procedure
7.1 Precautions: Selection of persons to make odor tests should be
carefully made. Extreme sensitivity is not required, but insensitive
persons should not be used. A good observer has a sincere interest
in the test. Extraneous odor stimuli such as those caused by smoking
and eating prior to the test or through the use of scented soaps,
perfumes, and shaving lotions must be avoided. The tester should be
free from colds or allergies that affect odor-response. Frequency of
tests must not be so great as to induce fatigue. Frequent rests in an
odor-free atmosphere are recommended.
The room in which the tests are to be conducted should be free
from distractions, drafts, and other odor. In certain industrial
atmospheres, a special odor-free room may be required, ventilated by
air filtered through activated carbon and maintained at a constant
(4")
comfortable temperature and humidity .
For precise work a panel of five or more testers should be used.
The persons making the odor measurements should not prepare the samples
and should not know the dilution concentrations being evaluated. These
302
-------
(Threshold Odor)
persons should have been made familiar with the procedure before
participating in a panel test. Always start with the most dilute
sample to avoid tiring the senses with the concentrated sample.
The temperature of the samples during testing should be kept within
1 degree of the specified temperature for the test.
7.2 Threshold Measurement: The ratio by which the odor-bearing sample
has to be diluted with odor-free water for the odor to be just
detectable by the odor test is the "threshold odor number" (T.O.).
The total volume of sample and odor-free water used in each test is
200 ml. The proper volume of odor-free water is put into the flask
first; the sample is then added to the water. Table 1 gives the
dilutions and corresponding threshold numbers.
Table 1. Threshold Odor Number Corresponding
to Various Dilutions
Sample Volume (ml)
Diluted to 200 ml
200
100
50
25
12.5
6.3
3.1
1.6
0.8
Threshold Odor
Number
1
2
4
8
16
32
64
128
256
7.3 Determine the approximate range of the threshold odor by:
7.3.1 Adding 200 ml, 50 ml, 12.5 ml, and 3.1 ml of the
sample to separate 500 ml glass-stoppered Erlenmeyer
flasks containing odor-free water to make a total volume
of 200 ml. A separate flask containing only odor-free water
serves as the reference for comparison. If run at 60°C, heat
303
-------
(Threshold Odor)
the dilutions and the reference in the constant temperature
bath to 60°C (±1°C).
7.3.2 Shake the flask containing the odor-free water, remove the
stopper, and sniff the vapors. Test the sample containing
the least amount of odor-bearing water in the same way. If
odor can be detected in this dilution, more dilute samples
must be prepared as described in 7.3.3. If odor cannot be
detected in the first dilution, repeat the above procedure
using the sample containing the next higher concentration of
the odor-bearing water, and continue this process until odor
is clearly detected.
7.3.3 If the sample being tested requires more extensive dilution
than is provided by Table 1, an intermediate dilution is
prepared from 20 ml of sample diluted to 200 ml with odor-free
water. Use this dilution for the threshold determination.
Multiply the T.O. obtained by ten to correct for the intermediate
dilution. In rare cases more than one tenfold intermediate
dilution step may be required.
7.4 Based on the results obtained in the preliminary test, prepare a set of
dilutions using Table 2 as a guide. One or more blanks are inserted in
the series, in the vicinity of the expected threshold, but avoiding any
repeated pattern. The observer does not know which dilutions are
odorous and which are blanks. He smells each flask in sequence, beginning
with the least concentrated sample and comparing with a known flask of
odor-free water, until odor is detected with utmost certainty.
304
-------
(Threshold Odor)
Table 2. Dilutions for Various Odor Intensities
Sample Volume in Which Odor First Noted
200 ml
50 ml
12.5 ml
3.1 ml
Volume (ml) of Sample to be Diluted to 200 ml
200
100
50
25
12.5
100
50
25
12.5
6.3
50
25
12.5
6.3
3.1
(Intermediate
Dilution,
See 7.3.3)
7.5 Record the observations of each tester by indicating whether odor is
noted (+ sign) in each test flask.
For example:
ml sample
diluted to 200 ml 12.5 0 25 0 50 100 200
Response + - + + +
8. Calculations
8.1 The threshold odor number is the dilution ratio at which odor is just
detectable. In the example above (7.5), the first detectable odor
occurred when 25 ml sample was diluted to 200 ml. Thus, the threshold
is 200 divided by 25, equals 8. Table 1 lists the threshold numbers
that correspond to common dilutions.
8.2 Anomalous responses sometimes occur; a low concentration may be called
positive and a higher concentration in the series may be called
negative. In such a case, the threshold is designated as that point of
detection after which no further anomalies occur. For instance:
ml sample
diluted to 200 ml
6.3
12.5 0 25 50 100
Response
-
threshold
305
-------
(Threshold Odor)
8.3 Calculations of panel results to find the most probable average
threshold are best accomplished by appropriate statistical methods.
For most purposes, the threshold of a group can be expressed as the
geometric mean (G.M.) of the individual thresholds. The geometric
mean is calculated in the following manner:
8.3,1 Obtain odor response as outlined in Procedure and record
results. For example:
Table 3. Sample Odor Series
ml of Odor- ml of
free Water Sample
188 12.5
175 25
200 ; 0
150 50
200 0
100 100
0 200
Observer Response*
1
-
-
^
-
+
+ •
2
.
®
-
4-
-
+
+
3
_
-
-
-
- -
^^
+
4
_
+
-
-
-
Q
+
5
_
©
-
+
-
+
+
*Circled plus equals threshold level.
8.3.2 Obtain individual threshold odor numbers from Table 1.
Observer
1
2
3
4
5
T.O.
4
8
2
2
8
8.3.3 The geometric mean is equal to the nth root of the product of
n numbers. Therefore:
4x8x2x2x8= 1024,
and
30103
and anti-log of 0.6021 = 4 = T.O.
9. Precision and Accuracy
9.1 Precision and accuracy data are not available at this time.
306
-------
(Threshold Odor)
9.2 A threshold number is not a precise value. In the case of the single
observer, it represents a judgment at the time of testing. Panel
results are more meaningful because individual differences have less
influence on the result. One or two observers can develop useful data
if comparison with larger panels has been made to check their sensi-
tivity. Comparisons of data from time to time or place to place should
not be attempted unless all test conditions have been carefully stand-
ardized and some basis for comparison of observer intensities exists.
References
1. Standard Methods, 13th Edition, Amer. Public Health Asso., New York, N.Y.
p. 248, Method 136 (1971).
2. ASTM, Comm E-18, STP 433, Basic Principles of Sensory Evaluation; STP 434,
Manual on Sensory Testing Methods; STP 440, Correlation of Subjective-
Objective Methods in the Study of Odors and Taste; Phil., Pennsylvania
(1968).
3. Standard Methods, 12th Ed., Amer. Public Health Asso., New York, N.Y., 1965,
p. 213.
4. Baker, R.A., "Critical Evaluation of Olfactory Measurement". Jour WPCF, 54,
582 (1962).
307
-------
TURBIDITY STORET No: QQQ70
1. Scope and Application
1.1 This method is applicable to surface and saline waters in the range
of turbidity from 0 to 40 Jackson units.
2. Summary of Method
2.1 The method is based upon a comparison of the intensity of light
scattered by the sample under defined conditions with the intensity
of light scattered by a standard reference suspension. The higher the
intensity of scattered light, the higher the turbidity. Readings, in
Jackson units, are made in a nephelometer designed according to
specifications outlined in Apparatus, 5. A standard suspension of
Formazin, also prepared under closely defined conditions, is used to
calibrate the instrument.
2.1.1 Formazin polymer is used as the turbidity reference suspension
for water because it is more reproducible than other types of
standards previously used for turbidity standards.
3. Sample Handling and Preservation
3.1 Samples taken for turbidity measurements should be analyzed as soon as
possible. Preservation of samples is not recommended.
4. Interferences
4.1 The presence of floating debris and coarse sediments which settle out
rapidly wiJl give false high readings. Finely divided air bubbles will
also affect the results in a positive manner.
4.2 The presence of true color, that is the color of water which is due to
dissolved substances which absorb light will cause turbidities to be
low, although this effect is generally not significant with finished
waters.
308
-------
(Turbidity)
5. Apparatus
5.1 The turbidimeter shall consist of a nephelometer with light source
for illuminating the sample and one or more photo-electric detectors
with a readout device to indicate the intensity of light scattered
at right angles to the path of the incident light. The turbidimeter
should be so designed that little stray light reaches the detector in
the absence of turbidity and should be free from significant drift
after a short warm-up period.
5.2 The sensitivity of the instrument should permit detection of turbidity
differences of 0.02 unit or less in waters having turbidities less than
1 unit. The instrument should measure from 0 to 40 units turbidity.
Several ranges will be necessary to obtain both adequate coverage and
sufficient sensitivity for low turbidities.
5.3 The sample tubes to be used with the available instrument must be of
clear, colorless glass. They should be kept scrupulously clean, both
inside and out, and discarded when they become scratched or etched.
They must not be handled at all where the light strikes them, but
should be provided with sufficient extra length, or with a protective
case, so that they may be handled.
5.4 Differences in physical design of turbidimeters will cause differences
in measured values for turbidity even though the same suspension is
used for calibration. To minimize such differences, the following
design criteria should be observed:
5.4.1 Light source: Tungsten lamp operated at not less than 85% of
rated voltage or more than rated voltage.
309
-------
(Turbidity)
5.4.2 Distance traversed by incident light and scattered light
within the sample tube: Total not to exceed 10 cm.
5.4.3 Angle of light acceptance of the detector: Centered at 90°
to the incident light path and not to exceed ±30° from 90°.
5.4.4 Maximum turbidity to be measured: 40 units.
5.5 At the time of this writing, the only instrument commercially available
with these specifications is the Hach Turbidimeter, Model 2100 and 2100A.
This instrument is recommended.
6. Reagents
6.1 Turbidity-free water - Pass distilled water through a 0.45 p pore
size membrane filter if such filter and water shows a lower turbidity
than the distilled Water.
6.2 Stock turbidity suspension:
Solution 1: Dissolve l.OOg hydrazine sulfate, (HN )_.H2S04, in
• distilled water and dilute to 100 ml in a volumetric flask.
Solution 2: Dissolve lO.OOg hexamethylenetetramine in distilled
water and dilute to 100 ml in a volumetric flask.
In a 100-ml volumetric flask, mix 5.0 ml Solution 1 with 5.0 ml
Solution 2. Allow to stand 24 hours at 25 ± 3°C, then dilute to the
mark and mix.
6.3 Standard turbidity suspension: Dilute 10.00 ml stock turbidity
suspension to 100 ml with turbidity-free water. The turbidity of
this suspension is defined as 40 units. Dilute portions of the standard
turbidity suspension with turbidity-free water as required.
6.3.1 A new stock turbidity suspension should be prepared each month.
The standard turbidity suspension and dilute turbidity standards
310
-------
(Turbidity)
should be prepared weekly by dilution of the stock turbidity
suspension.
7. Procedure
7.1 Turbidimeter calibration: The manufacturer's operating instructions
should be followed. Measure standards on the turbidimeter covering
the range of interest. If the instrument is already calibrated in
standard turbidity units, this procedure will check the accuracy of the
calibration scales. At least one standard should be run in each
instrument range to be used. Some instruments permit adjustments of
sensitivity so that scale values will correspond to turbidities.
Reliance on a manufacturer's solid scattering standard for
setting overall instrument sensitivity for all ranges is not an acceptable
practice unless the turbidimeter has been shown to be free of drift on
all ranges. If a pre-calibrated scale is not supplied, then calibration
curves should be prepared for each range of the instrument.
7.2 Turbidities less than 40 units: Shake the sample to thoroughly disperse
the solids. Wait until air bubbles disappear then pour the sample into
the turbidimeter tube. Read the turbidity directly from the instrument
scale or from the appropriate calibration curve.
7.3 Turbidities exceeding 40 units: Dilute the sample with one or more
volumes of turbidity-free water until the turbidity falls below 40 units.
The turbidity of the original sample is then computed from the turbidity
of the diluted spjnple and the dilution factor. For example, if 5 volumes
of turbidity-free water were added to 1 volume of sample, and the diluted
sample showed a turbidity of 30 units, then the turbidity of the
original sample was 180 units.
311
-------
(Turbidity)
7.3.1 The Hach Turbidimeters, Models 2100 and 2100A, are equipped
with 5 separate scales: 0-.02, 0-1.0, 0-10.0, 0-100, and
0-1000 JTU. It is strongly recommended, however, that the
upper scales be used as indications of required dilution
volumes to reduce readings to less than 40 JTU. (NOTE:
Comparative work performed in the AQC Laboratory indicates
a progressive error on sample turbidities in excess of
40 units.)
8. Calculation
8.1 Multiply sample readings by appropriate dilution to obtain final
reading.
8.2 Report results as follows:
Jackson Turbidity Record
Units to nearest:
0.0-1.0 0.05
1-10 0.1
10-40 1
40-100 5
100-400 10
400-1000 50
>1000 100
9. Precision and Accuracy
9.1 Precision and accuracy data are not available at this time.
312 * U. S. GOVERNMENT PRINTING OFFICE : 1911 O - 427-263
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