Method 349.0
Determination of Ammonia in Estuarine and Coastal Waters
by Gas Segmented Continuous Flow Colorimetric Analysis
Jia-Zhong Zhang, Cooperative Institute for Marine and Atmospheric Studies
Rosenstiel School of Marine and Atmospheric Science/AOML, NOAA
University of Miami, Miami, FL 33149
Peter B. Ortner, Charles J. Fischer, and Lloyd D. Moore, Jr., National Oceanic and
Atmospheric Administration, Atlantic Oceanographic and Meteorological Laboratory,
Ocean Chemistry Division, Miami, FL 33149
Project Officer
Elizabeth J. Arar
Version 1.0
September 1997
National Exposure Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
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Method 349.0
Determination of Ammonia in Estuarine and Coastal Waters
by Gas Segmented Continuous Flow Colorimetric Analysis
1.0	Scope and Application
1.1	This method provides a procedure for the
determination of ammonia in estuarine and coastal
waters. The method is based upon the indophenol
reaction,15 here adapted to automated gas-segmented
continuous flow analysis.
The term ammonia as used in this method denotes total
concentration of ammonia, including both chemical
forms, NH3 and NH4+. Because ionization of NH,+ has a
pK value of about 9.3, NH4+ is the dominant chemical
form in natural waters. At pH of 8.2 and 25°C only 8.1%
is present as NH3, the form that can be toxic to fish and
other aquatic organisms.
The concentration of ammonia in estuarine and coastal
water shows considerable temporal and spatial variability.
It rarely exceeds 0.005 mg N/L in oxygenated, unpolluted
estuarine and coastal water, but in anoxic water, the
amount of ammonia can be as high as 0.28 mg N/L.6
Although other forms of nitrogen contribute to primary
productivity and nutrient cycling in marine and estuarine
waters, ammonia is particularly important. Because
ammonia represents the most reduced form of inorganic
nitrogen available, it is preferentially assimilated by
phytoplankton. Whereas nitrate is the source of nitrogen,
it must first be reduced to ammonia before it can be
assimilated and incorporated into amino acids and other
compounds. Ammonia is released during the
decomposition of organic nitrogen compounds by
proteolytic bacteria, but also excreted directly by
invertebrates along with urea and peptides.7 In regions of
coastal upwelling, ammonia released by zooplankton can
play a significant role in supplying the nitrogen that
supports phytoplankton production.8
Chemical Abstracts Service
Analyte	Registry Numbers (CASRN)
Ammonia	7664-41-7
1.2	A statistically determined method detection limit
(MDL)9 of 0.3 |jg N/L has been determined by one
laboratory from seawaters of four different salinities. The
method is linear to 4.0 mg N/L using a Flow Solution
System (Alpkem, Wilsonville, Oregon).
1.3	Approximately 60 samples per hour can be
analyzed.
1.4	This method should be used by analysts both
experienced in the use of automated gas segmented
continuous flow colorimetric analyses, and also familiar
with matrix interferences and the procedures used in their
correction. A minimum of 6-months experience under the
close supervision of a qualified analyst is recommended.
2.0	Summary of Method
2.1	The automated gas segmented continuous flow
colorimetric method is used for the analysis of ammonia
concentration. Ammonia in solution reacts with alkaline
phenol and NaDTT (Sect. 7.2.5) at 60°C to form
indophenol blue in the presence of sodium
nitroferricyanide as a catalyst. The absorbance of
indophenol blue at 640 nm is linearly proportional to the
concentration of ammonia in the sample. A small
systematic negative error caused by differences in the
refractive index of seawater and reagent water, and a
positive error caused by the matrix effect on the color
formation, may be corrected for during data processing.
3.0	Definitions
3.1	Calibration Standard (CAL) — A solution
prepared from the primary dilution standard solution or
stock standard solution containing analytes. The CAL
solutions are used to calibrate the instrument response
with respect to analyte concentration.
3.2	Laboratory Fortified Blank (LFB) — An aliquot of
reagent water to which known quantities of the method
analytes are added in the laboratory. The LFB is analyzed
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exactly like a sample, and its purpose is to determine
whether method performance is within acceptable control
limits, and whether the laboratory is capable of making
accurate and precise measurements. This is a standard
prepared in reagent water that is analyzed as a sample.
3.3	Laboratory Fortified Sample Matrix
(LFM)- An aliquot of an environmental sample to which
known quantities of the method analytes are added in the
laboratory. The LFM is analyzed exactly like a sample,
and its purpose is to determine whether the sample matrix
contributes bias to the analytical results. The background
concentrations of the analytes in the sample matrix must
be determined in a separate aliquot and the measured
values in the LFM corrected for background
concentrations.
3.4	Laboratory Reagent Blank (LRB) — An aliquot of
reagent water that is treated exactly as a sample including
exposure to all labware, equipment, and reagents that are
used with other samples. The LRB is used to determine
if method analytes or other interferences are present in
the laboratory environment, the reagents, or apparatus.
3.5	Linear Dynamic Range (LDR) — The absolute
quantity or concentration range over which the instrument
response to an analyte is linear.
3.6	Method Detection Limit (MDL) — The minimum
concentration of an analyte that can be identified,
measured and reported with 99% confidence that the
analyte concentration is greater than zero.9
3.7	Reagent Water (RW) — Type 1 reagent grade
water equal to or exceeding the standards established by
the American Society for Testing and Materials (ASTM).
Reverse osmosis systems or distilling units followed by
Super-Q Plus Water System that produce water with 18
megohm resistance are examples of acceptable water
sources. To avoid contamination of ammonia from the air,
the reagent water should be stored in a sealed or a
collapsible container and used the day of preparation.
3.8	Refractive Index (Rl) — The ratio of the velocity
of light in a vacuum to that in a given medium. The
relative refractive index is the ratio of the velocity of light
in two different media, such as estuarine or sea water
versus reagent water. The correction for this difference is
referred to as refractive index correction in this method.
3.9	Stock Standard Solution (SSS) - A concentrated
solution of method analyte prepared in the laboratory
using assayed reference compounds or purchased from
a reputable commercial source.
3.10	Primary Dilution Standard Solution (PDS) — A
solution prepared in the laboratory from stock standard
solutions and diluted as needed to prepare calibration
solutions and other needed analyte solutions.
3.11	Quality Control Sample (QCS) — A solution of
method analyte of known concentrations which is used to
fortify an aliquot of LRB or sample matrix. The QCS is
obtained from a source external to the laboratory and
different from the source of calibration standards. It is
used to check laboratory performance with externally
prepared test materials.
3.12	Synchronization Peak Solution — A
synchronization peak is required by most data acquisition
programs to initialize the peak finding parameters. The
first cup in every run must always be identified as a SYNC
sample. The SYNC sample is usually a high
concentration standard, but can be any sample that
generates a peak at least 25% of full scale.
3.13	Color SYNC Peak Solution — A colored solution
used to produce a synchronization peak in the refractive
index measurement in which no color reagent is pumped
through system.
3.14	Sensitivity Drift — The change in absorbance for
a given concentration of analyte due to instrumental or
chemical drift during the course of measurement.
3.15	Matrix Effect — The change of absorbance in
different matrices due to the effect of ionic strength and
composition on the kinetics of color forming reactions.
4.0	Interferences
4.1	Hydrogen sulfide at concentrations greater than 2
mg S/L can negatively interfere with ammonia analysis.
Hydrogen sulfide in samples should be removed by
acidification with sulfuric acid to a pH of about 3, then
stripping with gaseous nitrogen.
4.2	The addition of sodium citrate and EDTA
complexing reagent eliminates the precipitation of
calcium and magnesium hydroxides when calcium and
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magnesium in seawater samples mix with high pH (about
13) reagent solution.4
4.3	Sample turbidity is eliminated by filtration or
centrifugation after sample collection.
4.4	As noted in Section 2.1 refractive index and salt
error interferences occur when sampler wash solution
and calibration standards are not matched with samples
in salinity, but are correctable. For low concentration
samples (< 20 |jg N/L), low nutrient seawater (LNSW)
with salinity matched to samples, sampler wash solutions
and calibration standards is recommended to eliminate
matrix interferences.
5.0	Safety
5.1	Water samples collected from the estuarine and
coastal environment are rarely hazardous. However, the
individual who collects samples should use proper
technique.
5.2	Good laboratory technique should be used when
preparing reagents. Laboratory personnel should obtain
material safety data sheets (MSDS) for al chemicals used
in this method. A lab coat, safety goggles, and gloves
should be worn when handling the concentrated acid.
5.3	Chloroform is used as a preservative in this
method. Use in a properly ventilated area, such as a fume
hood.
6.0	Equipment and Supplies
6.1	Gas Segmented Continuous Flow Autoanalyzer
Consisting of:
6.1.1	Automatic sampler.
6.1.2	Analytical cartridge with reaction coils and heater.
6.1.3	Proportioning pump.
6.1.4	Spectrophotometer equipped with a tungsten lamp
(380-800 nm) or photometer with a 640 nm interference
filter (maximum 2 nm bandwidth).
6.1.5	Strip chart recorder or computer based data
acquisition system.
6.1.6 Nitrogen gas (high-purity grade, 99.99%).
6.2 Glassware and Supplies
6.2.1	Gaseous ammonia concentration in the laboratory
air should be minimal to avoid sample or reagent
contamination. Remove any NH4OH solution stored in the
laboratory. Smoking should be strictly forbidden. An air
filtration unit might also be used to obtain ammonia-free
lab air.
6.2.2	All labware used in the analysis must be free of
residual ammonia to avoid sample or reagent
contamination. Soaking with laboratory grade detergent,
rinsing with tap water, followed by rinsing with 10% HCI
(v/v) and then thoroughly rinsing with reagent water was
found to be sufficient when working at moderate and high
concentration of ammonia. Ammonia is known for its high
surface reactivity.10 When working at low levels of
ammonia (< 20 |jg N/L), further cleaning of labware is
mandatory. Plastic bottles and glass volumetric flasks
should be cleaned in an ultrasonic bath with reagent
water for 60 minutes. Bottles and sample tubes made of
glass can be easily cleaned by boiling in reagent water.
Repeat the cleaning process with fresh reagent water
prior to use if necessary.
6.2.3	Automatic pipetters with disposable pipet tips
capable of delivering volumes ranging from 100 |jL to
1000 |jL and 1 mL to 10 mL.
6.2.4	Analytical balance, with accuracy to 0.1 mg, for
preparing standards.
6.2.5	60-mL glass or high density polyethylene sample
bottles, glass volumetric flasks and glass sample tubes.
6.2.6	Drying oven.
6.2.7	Desiccator.
6.2.8	Membrane filters with 0.45 |jm nominal pore size.
Plastic syringes with syringe filters.
6.2.9	Centrifuge.
6.2.10	Ultrasonic water bath cleaner.
7.0 Reagents and Standards
Note: All reagents must be of analytical reagent grade.
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7.1	Stock Reagent Solutions
7.1.1	Complexing Reagent - Dissolve 140 g of sodium
citrate dihydrate(Na3C6H507.2H20, FW 294.11), 5 g of
sodium hydroxide (NaOH, FW40) and 10 g ofdisodium
EDTA (Na2C10H14O8N2.2H2O, FW 372.24), in
approximately 800 mL of reagent water, mix and dilute to
1 L with reagent water. The pH of this solution is
approximately 13. This solution is stable for 2 months.
7.1.2	Stock Ammonium Sulfate Solution (100 mg N/L) -
Quantitatively transfer 0.4721 g of pre-dried (105°C for 2
hours) ammonium sulfate ((NH4)2S04, FW 132.15) to a
1000 mL glass volumetric flask containing approximately
800 mL of reagent water and dissolve the salt. Add a few
drops of chloroform as a preservative. Dilute the solution
to the mark with reagent water. Store in a glass bottle in
the refrigerator at 4°C. It is stable for 2 months.11
7.1.3	Low Nutrient Sea Water (LNSW) - Obtain natural
low nutrient seawater from surface water of the Gulf
Stream or Sargasso Sea (salinity 36 %o, < 7 |jg N/L) and
filter it through 0.3 micron pore size glass fiber filters. If
this is not available, commercial low nutrient sea water
( < 7 |jg N/L) with salinity of 35 %o (Ocean Scientific
International, Wormley, U.K.) can be substituted. NOTE:
Don't use artificial seawater in this method.
7.2	Working Reagents
7.2.1	Brij-35 Start-up Solution - Add 2 mL of Brij-35
surfactant (ICI Americas, Inc.) to 1000 mL reagent water
and mix gently.
Note: Brij-35 is a trade name for polyoxyethylene(23)
lauiyl ether (C^OCHjCH^OH, FW=1199.57, CASRN
9002-92-0).
7.2.2	Working Complexing Reagent- Add 1 mL Brij-35
to 200 mL of stock complexing reagent, mix gently.
Prepare this solution daily. This volume of solution is
sufficient for an 8-hour run.
7.2.3	Sodium Nitroferricyanide Solution - Dissolve 0.25
g of sodium nitroferricyanide (Na2Fe(CN)5N0.2H20, FW
297.97) in 400 mL of reagent water, dilute to 500 mL with
reagent water. Store in an amber bottle at room
temperature.
7.2.4	Phenol Solution - Dissolve 1.8 g of solid phenol
(C6H5OH, FW 94.11) and 1.5 g of sodium hydroxide
(NaOH, FW40) in 100 mL of reagent water. Prepare this
solution fresh daily.
7.2.5	NaDTT Solution - Dissolve 0.5 g of sodium
hydroxide (NaOH, FW40) and 0.2 g dichloroisocyanuric
acid sodium salt (NaDTT, NaC3CI2N303, FW 219.95) in
100 mL of reagent water. Prepare this solution fresh daily.
7.2.6	Colored SYNC Peak Solution - Add 50 |jL of blue
food coloring solution to 1000 mL reagent water and mix
thoroughly. Further dilute this solution to obtain a peak of
between 25 to 100 percent full scale according to the
AUFS setting used for refractive index measurement.
7.2.7	Primary Dilution Standard Solution - Prepare a
primary dilution standard solution (5 mg N/L) by diluting
5.0 mL of stock standard solution to 100 mL with reagent
water. Prepare this solution daily.
Note: This solution should be prepared to give an
intermediate concentration appropriate for further dilution
in preparing the calibration solutions. Therefore, the
concentration of a primary dilution standard solution must
be adjusted according to the desired concentration range
of calibration solutions.
7.2.8	Calibration Standards - Prepare a series of
calibration standards (CAL) by diluting suitable volumes
of a primary dilution standard solution (Section 7.2.7) to
100 mL with reagent water or low nutrient seawater.
Prepare these standards daily. The concentration range
of calibration standards should bracket the expected
concentrations of samples and not span more than two
orders of magnitude. At least five calibration standards
with equal increments in concentration should be used to
construct the calibration curve.
When working with samples of a narrow range of
salinities (± 2 %o) or samples containing low ammonia
concentration (< 20 |jg N/L), it is recommended that the
CAL solutions be prepared in Low Nutrient Seawater
(Section 7.1.4) diluted to the salinity of samples, and the
Sampler Wash Solution also be Low Nutrient Seawater
(Section 7.1.4) diluted to the same salinity. NOTE: If this
procedure is employed, it is not necessary to perform the
matrix effect and refractive index corrections outlined in
Sections 12.2 and 12.3.
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When analyzing samples of moderate and high ammonia
concentration (> 20 |jg N/L) with varying salinities,
calibration standard solutions and sampler wash
solutions can be prepared in reagent water. The
corrections for matrix effect and refractive index should be
subsequently applied (Sections 12.2 and 12.3).
7.2.9 Saline Ammonia Standards - If CAL solutions are
not prepared to match sample salinity, then saline
ammonia standards must be prepared in a series of
salinities in order to quantify the matrix effect (the change
in the colorimetric response of ammonia due to the
change in the composition of the solution). The following
dilution of Primary Dilution Standard Solution (Section
7.2.7) and LNSW with reagent water to 100 mL in
volumetric flasks, are suggested.
Salinity Volume of Volume of Cone.
(%0) LNSW(mL) PDS(mL)	mg N/L
0
0
2
.10
9
25
2
.10
18
50
2
.10
27
75
2
.10
35
98
2
.10
8.0	Sample Collection, Preservation and
Storage
8.1	Sample Collection - Samples collected for
nutrient analyses from estuarine and coastal waters are
normally collected using one of two methods: hydrocast
or submersible pump systems.
8.1.1	A hydrocast uses a series of sampling bottles
(Niskin, Go-Flo or equivalent) attached at fixed intervals to
a hydro wire. These bottles are sent through the water
column open and are closed either electronically or via a
mechanical messenger when the bottles have reached
the desired depth.
8.1.2	In a submersible pump system, a weighted hose
is sent to the desired depth in the water column and water
is pumped from that depth to the deck of the ship for
sample processing.
8.1.3	For collecting surface samples, an acid - cleaned
plastic bucket or a large plastic bottle can be used as
convenient samplers. Wash the sampler three times with
sample water before collecting samples.
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8.1.4	Turbid samples must be filtered through a 0.45
|jm membrane filter as soon as possible after collection.
Wash the filter with reagent water before use. Pass at
least 100 mL of sample through the filter and discard
before taking the final sample. Care must be taken to
avoid the contamination of ammonia especially handling
low concentrations of ammonia (< 20 |jg N/L) samples.10
An alternative technique to remove particulate is
centrifugation.
8.1.5	60-mL glass or high density polyethylene bottles
are used for sample storage. Sample bottles should be
rinsed 3 times with about 20 mL of sample, shaking with
the cap in place after each rinse. Pour the rinse water into
the cap to dissolve and rinse away salt crusts trapped in
the threads of the cap. Finally, fill the sample bottle about
3/4 full, and screw the cap on firmly.
8.2	Sample Preservation - After collection and
filtration or centrifugation, samples should be analyzed as
soon as possible. If samples will be analyzed within 3
hours then keep refrigerated in tightly sealed, glass or
high density polyethylene bottles in the dark at 4°C until
the analysis can be performed.
8.3	Sample Storage - At low concentrations of
ammonia (< 20 |jg N/L), no preservation technique is
satisfactory. Samples must be analyzed within 3 hours of
collection. At moderate and high concentrations of
ammonia (> 20 |jg N/L) samples can be preserved by the
addition of 2 mL of chloroform per liter of sample and
refrigerated in the dark at 4°C. Samples can be stored in
either glass or high density polyethylene bottles. A
maximum holding time for preserved estuarine and
coastal water samples with moderate to high
concentrations of ammonia is two weeks.12
9.0	Quality Control
9.1	Each laboratory using this method is required to
implement a formal quality control (QC) program. The
minimum requirements of this program consists of an
initial demonstration of performance, continued analysis
of Laboratory Reagent Blanks (LRB), laboratory
duplicates and Laboratory Fortified Blanks (LFB) with
each set of samples as a continuing check on
performance.
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9.2 Initial Demonstration of Performance
(Mandatory)
9.2.1	The initial demonstration of performance is used
to characterize instrument performance by determining
the MDL and LDR and laboratory performance by
analyzing quality control samples prior to analysis of
samples using this method.
9.2.2	A method detection limit (MDL) should be
established for the method analyte, using a low level
seawater sample containing, or fortified at, approximately
5 times the estimated detection limit. To determine MDL
values, analyze at least seven replicate aliquots of water
which have been processed through the entire analytical
method. Perform all calculations defined in the method
and report concentration in appropriate units. Calculate
the MDL as follows:
MDL = (t)(S)
where, S = the standard deviation of the
replicate analyses
t = Student's t value for n-1 degrees of
freedom at the 99% confidence
limit; t = 3.143 for six degrees
of freedom.
MDLs should be determined every 6 months or whenever
a significant change in background or instrument
response occurs or a new matrix is encountered.
9.2.3	The LDR should be determined by analyzing a
minimum of eight calibration standards ranging from
0.002 to 2.00 mg N/L across all sensitivity settings
(Absorbance Units Full Scale output range setting) of the
detector. Standards and sampler wash solutions should
be prepared in low nutrient seawater with salinities similar
to that of samples to avoid the necessity to correct for salt
error, or refractive index. Normalize responses by
multiplying the response by the Absorbance Units Full
Scale output range setting. Perform the linear regression
of normalized response vs. concentration and obtain the
constants m and b, where m is the slope and b is the y-
intercept. Incrementally analyze standards of higher
concentration until the measured absorbance response,
R, of a standard no longer yields a calculated
concentration Cc, that is within 100 ± 10% of known
concentration, C, where Cc = (R-b)/m. That concentration
defines the upper limit of the LDR for the instrument.
Should samples be encountered that have a
concentration that is > 90% of the upper limit of LDR,
then these samples must be diluted and reanalyzed.
9.3 Assessing Laboratory Performance
(Mandatory)
9.3.1	Laboratory Reagent Blank (LRB) - A laboratory
should analyze at least one LRB with each set of
samples. LRB data are used to assess contamination
from the laboratory environment. Should an analyte value
in the LRB exceed the MDL, then laboratory or reagent
contamination should be suspected. When the LRB value
constitutes 10% or more of the analyte concentration
determined for a sample, duplicates of the sample must
be prepared and analyzed again after the source of
contamination has been corrected and acceptable LRB
values have been obtained.
9.3.2	Laboratory Fortified Blank (LFB) - A laboratory
should analyze at least one LFB with each set of
samples. The LFB must be at a concentration within the
daily calibration range. The LFB data are used to
calculate accuracy as percent recovery. If the recovery of
the analyte falls outside the required control limits of 90
-110%, the source of the problem should be identified
and resolved before continuing the analyses.
9.3.3	The laboratory must use LFB data to assess
laboratory performance against the required control limits
of 90 -110%. When sufficient internal performance data
become available (usually a minimum of 20 to 30
analyses), optional control limits can be developed from
the percent mean recovery (x) and standard deviation (S)
of the mean recovery. These data can be used to
establish the upper and lower control limits as follows:
Upper Control Limit = x + 3S
Lower Control Limit = x - 3S
The optional control limits must be equal to or better than
the required control limits of 90-110%. After each 5 to 10
new recovery measurements, new control limits can be
calculated using only the most recent 20 to 30 data
points. Also the standard deviation (S) data should be
used to establish an ongoing precision statement for the
level of concentrations included in the LFB. These data
must be kept on file and available for review.
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9.4 Assessing Analyte Recovery -Laboratory
Fortified Sample Matrix (LFM)
9.4.1	A laboratory should add a known amount of
analyte to a minimum of 5% of the total number of
samples or one LFM per sample set, whichever is
greater. The analyte added should be 2-4 times the
ambient concentration and should be at least four times
greater than the MDL.
9.4.2	Calculate percent recovery of analyte, corrected
for background concentration measured in a separate
unfortified sample. These values should be compared
with the values obtained from the LFBs. Percent
recoveries may be calculated using the following
equation:
(Cs-C)
R =	X 100
S
where, R = percent recovery
Cs = measured fortified sample
addition in mg N/L
C = sample background
concentration (mg N/L)
S = concentration in mg N/L added
to the environmental sample.
9.4.3	If the recovery of the analyte falls outside the
required control limits of 90-110%, but the laboratory
performance for that analyte is within the control limits,
the fortified sample should be prepared again and
analyzed. If the result is the same after reanalysis, the
recovery problem encountered with the fortified sample is
judged to be matrix related and the sample data should
be flagged accordingly.
10.0	Calibration and Standardization
10.1	At least five calibration standards should be
prepared fresh daily for system calibration.
10.2	A calibration curve should be constructed for
each sample set by analyzing a series of calibration
standard solutions. A sample set should contain no more
than 60 samples. For a large number of samples make
several sample sets with individual calibration curves.
10.3	Analyze the calibration standards, in duplicate,
before the actual samples.
10.4	The calibration curve containing five data points
or more that bracket the conentrations of samples should
have a correlation coefficient, r, of 0.995 or better and the
range should not be greater than two orders of
magnitude.
10.5	Use a high CAL solution followed by two blank
cups to quantify system carryover. The difference in peak
heights between two blank cups is due to the carryover
from the high CAL solution. The carryover coefficient, k,
is calculated as follows:
P - P
rb1 rb2
k=	
P
1 high
where, Phigh = the peak height of the high
ammonia standard
Pb1 = the peak height of the
first blank sample
Pb2 = the peak height of the
second blank sample
The carryover coefficient, k, should be measured in seven
replicates to obtain a statistically significant number. The
carryover coefficient should be remeasured with any
change in manifold plumbing or upon replacement of
pump tubes.
The carryover correction (CO) of a given peak, i, is
proportional to the peak height of the preceding sample,
Pm-
CO = (k)x(PM)
To correct a given peak height reading, P,, subtract the
carryover correction.1314
P, c = P, - CO
where Pic is corrected peak height. The correction for
carryover should be applied to all the peak heights
throughout a run. The carryover coefficient should be less
than 5% in this method.
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10.6 Place a high standard solution at the end of each
sample run to check for sensitivity drift. Apply sensitivity
drift correction to all the samples. The sensitivity drift
during a run should be less than 5%.
Note: Sensitivity drift correction is available in most data
acquisition software supplied with autoanalyzers. It is
assumed that the sensitivity drift is linear with time. An
interpolated drift correction factor is calculated for each
sample according to the sample position during a run.
Multiply the sample peak height by the corresponding
sensitivity drift correction factor to obtain the corrected
peak height for each sample.
11.0	Procedure
11.1	If samples are stored in a refrigerator, remove
samples and equilibrate to room temperature prior to
analysis.
11.2	Turn on the continuous flow analyzer and data
acquisition components and warm up at least 30 minutes.
11.3	Set up cartridge and pump tubes as shown in
Figure 1.
11.4	Set spectrophotometer wavelength to 640 nm,
and turn on lamp.
11.5	Set the Absorbance Unit Full Scale (AUFS) range
on the spectrophotometer at an appropriate setting
according to the highest concentration of ammonia in the
samples. The highest setting appropriate for this method
is 0.2 AUFS for 6 mg N/L.
11.6	Prepare all reagents and standards.
11.7	Choose an appropriate wash solution for sampler
wash. For analysis of samples with a narrow range of
salinities (± 2 %o) or for samples containing low ammonia
concentrations (< 20 |jg N/L), it is recommended that the
CAL solutions be prepared in Low Nutrient Seawater
(Section 7.1.4) diluted to the salinity of samples, and that
the Sampler Wash Solution also be Low Nutrient
Seawater diluted to the same salinity. For samples with
varying salinities and higher ammonia concentrations (>
20 |jg N/L), it is suggested that the reagent water used for
the sampler wash solution and for preparing calibration
standards and procedures in Section 12.2 and 12.3 be
employed.
11.8	Begin pumping the Brij-35 start-up solution
(Section 7.2.1) through the system and obtain a steady
baseline. Place the reagents on-line. The reagent
baseline will be higher than the start-up solution baseline.
After the reagent baseline has stabilized, reset the
baseline.
Note: To minimize the noise in the reagent baseline,
clean the flow system by sequentially pumping the
sample line with reagent water, 1 N HCI solution, reagent
water, 1 N NaOH solution for few minutes each at tahe
end of the daily analysis. Make sure to rinse the system
well with reagent water after pumping NaOH solution to
prevent precipitation of Mg(OH)2 when seawater is
introduced into the system. Keep the reagents and
samples free of particulate. Filter the reagents and
samples if necessary.
If the baseline drifts upward, pinch the waste line for a few
seconds to increase back pressure. If absorbance drops
down rapidly when back pressure increases, this indicates
that there are air bubbles trapped in the flow cell. Attach
a syringe at the waste outlet of the flowcell. Air bubbles
in the flowcell can often be eliminated by simply attaching
a syringe for a few minutes or, if not, dislodged by
pumping the syringe piston. Alternatively, flushing the
flowcell with alcohhol was found to be effective in
removing air bubbles from the flowcell.
11.9	The sampling rate is approximately 60 samples
per hour with 30 seconds of sample time and 30 seconds
of wash time.
11.10	Use cleaned sample cups or tubes (follow the
procedures outlined in Section 6.2.2). Place CAL
solutions and saline standards (optional) in sampler.
Complete filling the sampler tray with samples, laboratory
reagent blanks, laboratory fortified blanks, laboratory
fortified sample matrices, and QC samples. Place a blank
after every ten samples.
11.11	Commence analysis.
12.0	Data Analysis and Calculations
12.1	Concentrations of ammonia in samples are
calculated from the linear regression, obtained from the
standard curve in which the concentrations of the
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calibration standards are entered as the independent
variable, and their corresponding peak heights are the
dependent variable.
12.2 Refractive Index Correction for Estuarine and
Coastal Samples
12.2.1	If reagent water is used as the wash solution, the
operator has to quantify the refractive index correction
due to the difference in salinity between sample and wash
solution. The following procedures are used to measure
the relationship between the sample salinity and refractive
index on a particular detector.
12.2.2	First, analyze a set of ammonia standards in
reagent water with color reagent using reagent water as
the wash and obtain a linear regression of peak height
versus concentration.
12.2.3	Second, replace reagent water wash solution with
Low Nutrient Seawater wash solution.
Note: In ammonia analysis absorbance of the reagent
water is higher than that of the LNSW. When using
reagent water as a wash solution, the change in refractive
index causes the absorbance of seawater to become
negative. To measure the absorbance due to refractive
index change in different salinity samples, Low Nutrient
Seawater must be used as the wash solution to bring the
baseline down.
12.2.4	Third, replace the phenol solution (Section 7.2.4)
and NaDTT solution (Section 7.2.5) with reagent water.
All other reagents remain the same. Replace the
synchronization sample with the colored SYNC peak
solution (Section 7.2.6).
12.2.5	Prepare a series of different salinity samples by
diluting the LNSW. Commence analysis and obtain peak
heights for different salinity samples. The peak heights for
the refractive index correction must be obtained at the
same AUFS range setting and on the same
spectrophotometer as the corresponding standards
(Section 12.2.2).
12.2.6	Using LNSW as the wash water, a maximum
absorbance will be observed for reagent water. No
change in refractive index will be observed in the
seawater sample. Assuming the absolute absorbance for
reagent water (relative to the seawater baseline) is equal
to the absorbance for seawater (relative to reagent water
baseline), subtract the absorbances of samples of various
salinities from that of reagent water. The results are the
apparent absorbance due to the change in refractive
index between samples of various salinities relative to the
reagent water baseline.
12.2.7	For each sample of varying salinity, calculate the
apparent ammonia concentration due to refractive index
from its peak height corrected to reagent water baseline
(Section 12.2.5) and the regression equation of ammonia
standards obtained with color reagent being pumped
through the system (Section 12.2.2). Salinity is entered as
the independent variable and the apparent ammonia
concentration due to refractive index is entered as the
dependent variable. The resulting regression allows the
operator to calculate apparent ammonia concentration
due to refractive index when the sample salinity is known.
Thus, the operator would not be required to obtain
refractive index peak heights for all samples.
12.2.8	The magnitude of refractive index correction can
be minimized by using a low refractive index flowcell. An
example of a typical result using a low refractive index
flowcell follows:
Salinity	Apparent ammonia conc. due
(%0)	to refractive index (|jg N/L)
0.0
0.00
4.5
0.18
9.1
0.45
13.9
0.66
17.9
0.86
27.6
1.30
36.2
1.63
Note: You must calculate the refractive index correction
for your particular detector. The refractive index must be
redetermined whenever a significant change in the design
of the flowcell or a new matrix is encountered.
12.2.9 An example of a typical equation is:
Apparent ammonia (|jg N/L) = 0.0134 + 0.0457S
where S is sample salinity in parts per thousand. The
apparent ammonia concentration due to refractive index
so obtained should then be added to samples of
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corresponding salinity when reagent water was used as
the wash solution for samples analysis.
If a low refractive index flowcell is used and ammonia
concentration is greater than 200 |jg N/L, the correction
for refractive index becomes negligible.
12.3 Correction for Matrix Effect in Estuarine and
Coastal Samples
12.3.1	When calculating concentrations of samples of
varying salinities from standards and wash solution
prepared in reagent water, it is necessary to first correct
for refractive index errors, then correct for the change in
color development due to the differences in composition
between samples and standards (matrix effect). Even
where the refractive index correction may be small, the
correction for matrix effect can be appreciable.
12.3.2	Plot the salinity of the saline standards (Section
7.2.9) as the independent variable, and the apparent
concentration of ammonia (mg N/L) from the peak height
(corrected for refractive index) calculated from the
regression of standards in reagent water, as the
dependent variable for all saline standards. The resulting
regression equation allows the operator to correct the
concentrations of samples of known salinity for the color
enhancement due to matrix effect. An example of a
typical result follows:
Peak height of UncorrectedNH3
Salinity	0.140 mg N/L conc. calculated
(%0)	from standards
in reagent water
(mg N/L)
0
2420
0.1400
4.5
2856
0.1649
9.1
2852
0.1649
13.9
2823
0.1635
17.9
2887
0.1673
27.6
2861
0.1663
36.2
2801
0.1633
12.3.3 Using the reagent described in Section 7.0, as
shown above, matrix effect becomes a single factor
independent of sample salinity. An example of a typical
equation to correct for matrix effect is:
Corrected concentration (mg N/L)
= Uncorrected concentration /1.17(mg N/L)
12.3.4 Results of sample analyses should be reported
in mg N/L or in |jg N/L.
mg N/L = ppm (parts per million)
|jg N/L = ppb (part per billion)
13.0	Method Performance
13.1	Single Laboratory Validation
13.1.1 Method Detection Limit- A method detection limit
(MDL) of 0.3 |jg N/L has been determined by one
laboratory from spiked LNSW of three different salinities
as follows:
Salinity [NH3] SD Recovery MDL
(%0) (|jg N/L) (Mg N/L) (%) (M9 N/L)
36.2
0.7
0.0252
95.4
0.0792
36.2
0.7
0.0784
100.8
0.2463
36.2
1.4
0.0826
104.7
0.2595
36.2
1.4
0.0966
105.6
0.3035
17.9
0.7
0.0322
106.5
0.1012
17.9
0.7
0.0182
92.2
0.0572
17.9
1.4
0.0938
109.1
0.2947
17.9
1.4
0.0882
100
0.2771
4.5
0.7
0.0672
95.1
0.2111
4.5
1.4
0.1008
94.1
0.3167
4.5
1.4
0.126
106.7
0.3959
0.0
0.7
0.077
98.2
0.2419
0.0
0.7
0.0784
100.8
0.2463
0.0
1.4
0.0854
101.9
0.2683
13.1.2 Single Analyst Precision - A single laboratory
analyzed three samples collected from the Miami River
and Biscayne Bay, Florida. Seven replicates of each
sample were processed and analyzed with salinity
ranging from 4.8 to 35.0. The results were as follows:
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Sample
Salinity
Concentration
RSD

(%o)
(Mg N/L)
(%)
1
35.5
6.3
7.19
2
20.0
72.1
1.57
3
4.8
517.6
0.64
13.1.3 Laboratory Fortified Sample Matrix - Laboratory
fortified sample matrices were processed in three
different salinities ranging from 4.8 to 35.0 and ambient
ammonia concentrations from 0.0 to 72.1 |jg N/L. Seven
replicates of each sample were analyzed and the results
were as follows:
Salinity Concentration RSD Recovery
ambient fortified
(%0)	(|jg N/L)	(%) (%)
35.5 6.3	70 5.01 98.3
20.0 72.1 140 1.71 98.3
4.8 0.0	280 1.81 98.1
13.1.4	Linear Dynamic Range - A linear dynamic range
(LDR) of 4.0 mg N/L has been determined by one
laboratory from spiked LNSW using a Flow Solution
System (Alpkem, Wilsonville, Oregon).
13.1.5	Sample Preservation Study - Natural samples
have been preserved by freezing, acidification and
addition of chloroform and phenol as preservatives to the
samples stored in glass and high density polyethylene
bottles. Table 1 summarized the results of preservation
study.
There is no significant difference in recovery of ammonia
from samples stored in glass and high density
polyethylene bottles, suggesting either glass or high
density polyethylene bottles can be used for storage of
ammonia samples.
For low concentration of ammonia samples (< 20 |jg N/L,
sample 1 in table 1), no preservation technique is
satisfactory. Samples must be analyzed within 3 hours of
collection.
Freezing cannot preserve ammonia in samples for more
than one week. Acidified samples must be neutralized
with NaOH solution prior to analysis. Addition of NaOH to
acidified samples induces the precipitation of Mg(OH)2
and Ca(OH)2. Centrifuging the samples cannot
completely eliminate the interference, therefore,
acidification is not suitable preservation technique.
Addition of phenol increases the absorbance of samples.
Phenol is not recommended as a suitable preservative
although samples preserved with phenol were stable as
those preserved by chloroform.12
For moderate and high concentrations of ammonia (> 20
|jg N/L) samples, it is suggested samples be preserved
by the addition of 2 mL of chloroform per liter of sample
and refrigerated in the dark at 4°C. A maximum holding
time for preserved estuarine and coastal water samples
with moderate to high concentrations of ammonia is two
weeks.10
13.2 Multi-Laboratory Validation
Multi-laboratory data is unavailable at this time.
14.0	Pollution Prevention
14.1	Pollution prevention encompasses any technique
that reduces or eliminates the quantity or toxicity of waste
at the point of generation. Numerous opportunities for
pollution prevention exist in laboratory operation. The
USEPA has established a preferred hierarchy of
environmental management techniques that places
pollution prevention as the management option of first
choice. Whenever feasible, laboratory personnel should
use pollution prevention techniques to address their waste
generation. When wastes cannot be feasibly reduced at
the source, the agency recommends recycling as the next
best option.
14.2	For information about pollution prevention that
may be applicable to laboratories and research
institutions, consult Less is Better: Laboratory Chemical
Management for Waste Reduction, available from the
American Chemical Society, Department of Government
Relations and Science Policy, 1155 16th Street N.W.,
Washington D.C. 20036, (202) 872-4477.
15.0	Waste Management
15.1	The U.S. Environmental Protection Agency
requires that laboratory waste management practices be
conducted consistent with all applicable rules and
regulations. The Agency urges laboratories to protect the
air, water, and land by minimizing and controlling all
releases from hoods and bench operations, complying
with the letter and spirit of any sewer discharge permits
and regulations, and by complying with all solid and
hazardous waste regulations, particularly the hazardous
waste identification rules and land disposal restrictions.
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349.0-12

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For further information on waste management consult
The Waste Management Manual for Laboratory
Personnel, available from the American Chemical Society
at the address listed in Section 14.2.
16.0 References
1.	Solorzano, L. 1969. Determination of ammonia in
natural waters by the phenylhypochlorite method.
Limnol. Oceanogr., 14:799-801.
2.	Head, P.C., 1971. An automated
phenolhypochlorite method for the determination of
ammonia in sea water. Deep-Sea Research,
18:531-532.
3.	Slawyk, G., and Maclsaac, J.J., 1972. Comparison
of two automated ammonia methods in a region of
coastal upwelling. Deep-Sea Research, 19:521-
524.
4.	Hansen, H.P. and Grasshoff, K. 1983, Automated
Chemical Analysis, In Methods of Seawater
Analysis (Grasshoff, K., M. Ehrhardt and K.
Kremling, Eds) Weinheim, Verlag Chemie,
Germany. pp363-365.
5.	Mautoura, R.F.C. and E.M.S. Woodward, 1983.
Optimization of the indophenol blue method for the
automated determination of ammonia in estuarine
waters. Estuarine, Coastal and Shelf Science,
17:219-224.
6.	Zhang J-Z, and F. J. Millero 1993. The chemistry of
anoxic waters in the Cariaco Trench. Deep-Sea
Res., 40:1023-1041.
7.	Raymont, J.E.G. 1980. Plankton and productivity in
the oceans. Pergamon Press, Oxford, England.
8.	Smith, S.L. and T.E. Whitledge. 1977. The role of
zooplankton in the regeneration of nitrogen in a
coastal upwelling off northwest Africa. Deep-Sea
Res. 24: 49-56.
9.	Code of Federal Regulations 40, Ch. 1, Pt. 136
Appendix B. Definition and Procedure for the
Determination of Method Detection Limit. Revision
1.11.
10.	Eaton, A.D. and V. Grant, 1979. Sorption of
ammonium by glass frits and filters: implications for
analyses of blakish and freshwater. Limnol.
Oceanogr. 24:397-399.
11.	Aminot A. and R. Kerouel, 1996. Stability and
preservation of primary calibration solutions of
nutrients. Mar. Chem. 52:173-181.
12.	Degobbis, D. 1973. On the storage of seawater
samples for ammonia determination. Limnol.
Oceanogr., 18:146-150.
13.	Angelova, S, and H.W.Holy. 1983. Optimal speed
as a function of system performance for continuous
flow analyzers. Analytica Chimica Acta, 145:51-58.
14.	Zhang, J.-Z. 1997. Distinction and quantification of
carry-over and sample interaction in gas
segmented continuous flow analysis. Journal of
Automatic Chemistry, 19(6):205-212.
349.0-13
Version 1.0 September 1997

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17.0 Tables, Diagrams, Flowcharts, and Validation Data
Debubbler
m <
To Waste
O
Detector
640nm
60t
Coil
N /

fo Waste
o ^
10 O- -|-
_0_ _Q_
-8-<^
6
-Qz
x;©
o 3
2 QZ
Heater
60°C
Manifold
Wash To Sampler



-f

0.41
0.41
0.10
0.10
0.10
1.01
0.25
0.32
1.57
Nitroferricyanide
NaDTT
Phenol
H
Sample
Nitrogen
Complexing Reagent
Reagent Water
or Low Nutrient Seawater
Pump
mL/min
Sample:Wash = 30":30"
Figure 1. Manifold Configuration for Ammonia Analysis.
Version 1.0 September 1997
349.0-14

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Table 1 . Percentage RecoveryA of Ammonia From Natural Water Samples Preserved by Freezing, Acidification,
Addition of Chloroform and Phenol.
sample8
method0
bottle0
0
7
time (day)
14
21
28
1
none
HDPE
100
349
345
18
91

freezing
glass
100
100
0
0
0


HDPE
100
102
0
0
0

h2so4e
glass
200
564
285
73
55


HDPE
200
113
64
45
36

CHCIj
glass
193
135
29
47
36


HDPE
193
193
18
44
36

phenolF
glass
153
36
44
0
0


HDPE
153
36
0
0
0
1 +
freezing
glass
100
101
82
77
102


HDPE
100
97
76
61
81

h2so4e
glass
95
105
69
54
37


HDPE
95
91
91
88
116

CHCIj
glass
96
105
85
78
89


HDPE
96
102
85
78
92

phenolF
glass
130
133
110
148
123


HDPE
130
128
102
103
118
2
none
HDPE
100
32
0
0
0

freezing
glass
100
109
93
77
88


HDPE
100
107
82
67
91

h2so4e
glass
252
162
66
62
50


HDPE
252
193
45
41
27

CHCIj
glass
99
114
83
75
96


HDPE
99
98
80
70
83

phenolF
glass
108
107
88
74
93


HDPE
108
101
83
74
86
2+
freezing
glass
99
108
109
111
106


HDPE
99
106
95
78
91

h2so4e
glass
100
107
51
86
88


HDPE
100
102
39
98
107

CHCIj
glass
99
106
116
94
105


HDPE
99
107
98
95
103

phenolF
glass
117
121
106
105
116


HDPE
117
124
107
106
117
3
none
HDPE
100
104
14
1
0

freezing
glass
100
-
116
64
106


HDPE
100
108
105
65
75

h2so4e
glass
101
106
44
74
61


HDPE
101
108
111
106
109

CHCIj
glass
100
96
98
96
94


HDPE
100
93
97
95
95

phenolF
glass
112
106
107
112
125


HDPE
112
112
108
110
112
Recovery is calculated based on the ammonia concentration in non-preserved sample at day 0. Samples with
recoveries higher than 100% are subject to interference either from precipitation or phenol.
For salinity and concentration of ammonia in samples 1,2,3 see Section 13.1.2.
349.0-15
Version 1.0 September 1997

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Sample 1+ and 2+ are the fortified samples 1 and 2 at ammonia concentrations 76.3 and 202.1 |jg N/L,
respectively.
Methods of preservation:
None: stored the samples in high density polyethylene carboys at room temperature without any
preservative added.
Freezing: Frozen and stored at -20°C.
H2S04: Acidified to pH 1.8 with H2S04, and stored at 4°C. Neutralized the acid with
NaOH solution before analysis.
CHCI3: Added 2 mL chloroform per 1000 mL sample, and stored at 4°C.
Phenol: Added 8 g phenol per 1000 mL sample, and stored at 4°C.
Glass and high density polyethylene bottles were compared to determine the effect of sample
bottle type on the preservation.
Adding NaOH to neutralize acidified samples induced the precipitation of Mg(OH)2 and Ca(OH)2.
Centrifuging the samples can not completely eliminate the interference, therefore, acidification is
not suitable preservation technique.
Although samples preserved with phenol were stable as those preserved by chloroform,
an absorbance increase was observed, therefore, this is not recommended as a suitable
preservation technique.
Version 1.0 September 1997	349.0-16

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