-------
REFERENCES
1. Robson, C. D. and K. E. Foster, "Evaluation of Air Participate
Sampling Equipment," Am. Ind. Hyg. Assoc J. 24, 404 (1962)
2. Tierney, G. P. and W. D. Conner, "Hygroscopic Effects on Weight
Determination of Particulates Collected on Glass-Fiber Filters,"
Am. Ind. Hyg. Assoc J. 28, 363, (1967)
3. McKee, Herbert C., Ralph E. Childers and Oscar Saeng, Jr.,
"Collaborative Study of Reference Method for the Determination of
Suspended Particulates in the Atmosphere (High Volume Method),"
Published by Southwest Research Institute, San Antonio, Texas,
June 1971, Under EPA Contract #70-40.
4. Harrison, W. K., J. S. Nader and F. S. Fugman, "Constant Flow
Regulators for High-Volume Air Sampler," Am. Ind. Hyg. Assoc. J.
21, 114-120 (1960).
5. Much material used is from the Federal Register, Vol. 36, No. 228,
Thursday, Nov. 25, 1971.
22
-------
I.b. SUSPENDED NITRATES (SN)
23
-------
I.b. SUSPENDED NITRATES (SN)
1. Principle and Applicability
1.1 Suspended nitrates are collected on the hi-vol filter
(Reference Sect. 1.0). Nitrate concentrations are
determined by analyzing a portion of the exposed
filter.
A strip of the filter is put into a flask with
distilled water and refluxed. The extracted water
soluble nitrates are reduced to nitrites by a copper-
cadmium reductor column. The nitrite ion is reacted
with sulfanilamide in acidic solution to form a diazo
compound. This compound then couples with a N-l-
naphthylene-diamine dihydrochloride to form a reddish-
purple dye. They dye concentration, proportional to
nitrate concentration, is determined spectrophotometri-
cally at 540 nm.
1.2 Applicability. This method applies to the analysis of
sulfates collected with the 24-hour hi-vol sampler.
2. Range and Sensitivity
The analysis method applies from 0.5 to 30.0 ug N03~/ml.
3. Interferences
Metal ions can produce a positive error, i.e., divalent
mercury and divalent copper can form colored complex ions
with absorption bands in the region of color measurement.
24
-------
4. Precision and Accuracy
Precision and accuracy depend upon the region of the
absorbance vs. concentration curve in which work is being
done. Accuracies range between 3 and 10 percent.
5. Sampling Apparatus
Sampling apparatus is the hi-volume sampler described in
the TSP procedure. (Reference Section 1).
6. Sampling Procedure
Sampling procedures are the same as in Section 6.1 in the
TSP procedure. (Reference Section 1).
7. Analysis
7.1 Apparatus
7.1.1 Volumetric flasks, pipets, beakers, and grad-
uated cylinders to prepare solutions. Use
Class A glassware.
7.1.2 Vacuum Filtering Apparatus. Device which
permits vacuum filtering directly into the
receiver. This consists of a bell jar with a
top opening, a side tabulation and a bottom plate.
The Buchner funnel passes through the top opening
and is sealed to the bell jar with a stopper.
The bell jar should be tall enough to contain
the polyethylene bottles used for storing the
samples. The vacuum connection is made using
the side tabulation. The filtering apparatus
is shown in Figure 1.
25
-------
Suchner Funnel with
Fritted Disc
To Vacuum
Pump
Polyethylene
Bottle
Bell Jar
Baseplate
Figure 1 - Vacuum Filtering Apparatus
26
-------
7.1.3 Vacuum Pump. Any device which can maintain a
vacuum of at least 64 cm of Hg. Mechanical pumps
or water aspirators may be used.
7.1.4 Polyethylene Bottles. Bottles with a capacity of
60 ml (2 oz) fitted with polyseal caps.
7.1.5 pH Meter. Capable of measuring pH to nearest
0.1 pH units over a range of 0-14.
7.1.6 Glass Bottles (brown). 500 ml glass bottles with
polyseal caps.
7.1.7 Pump Tubing. Flow rated tubing of the capacities
shown in Figure 2. Silicone rubber tubing in
place of the standard pump tubing is highly
recommended. Standard pump tubing should be
replaced every day if used. Other available
tubing has correspondingly longer life (3 weeks)
with silicone rubber tubing having performed
satisfactorily for as long as 5 weeks. If a
plasticized tubing is used, it should be washed
with acetone followed by distilled water prior
to its use.
7.1.8 Erlenmeyer Flask. 125 ml with 24/40 joint.
7.1.9 Condenser. Water jacketed, 300 mm length with
24/40 joints.
7.1.10 Hot Plate. Suitable for sample extraction
(7.2.1).
7.1.11 Pyrex Glass Wool.
27
-------
Figure 2 -NITRATE AND NITRITE IN WATER
DEE
WAJ
/
COLORIMETER (
540 nm
3UBBLEF
iTeFF
(l IT-
\
^
A
1 | 5 TURNS
T^l 00010
EDUCTOR TUBE
20 TURNS
nnnnnn ,
_ UUUUUl/
^> TO F/C
rumr lubt
1 5 mm F/C x 2.0 mm ID
WASTE -
^ BLK/BLK (0.32) AIR
W AMMONIUM CHLORIDE
YFI /YFI /1 ?n^
U
x^ BLK/BLK (0.32) SAMPLE
^
I ^^ BLK/BLK (0.32) AIR
I
I
COI OR RFAfiFNIT
^v BLK/BLK (0.32)
_ ^^ WHT/WHT (0.60)
(o O °)
SAMPLER IV
40/HR4:1
TO SAMPLER IV
WASH RECEPTACLE
WASTE
GRN/GRN (2.00) WATER
GRY/GRY (1.00) FROM F/C
NOTE: FIGURES IN PARENTHESES
SIGNIFY FLOW RATES IN
ML/MIN. FLOW RATES ARE
COLOR-CODED.
*0.034 POLYETHYLENE
28
-------
7.1.12 Plastic Tubing. 10 cm (3.94 in) and 2.3 mm
(0.09 in) I.D. Polyvinylchloride tubing, for
ion exchange column (5.2.1.5).
7.1.13 Rubber Pi pet Bulb.
7.1.14 Buchner Funnels. Buchner style 150 ml capacity
with finepore fritter glass filter.
7.1.15 Instrument. Technicon Autoanalyzer II as
listed below:
a. Sample turntable with variable sample
rate and variable sample to wash ratio.
b. Proportioning pump: flow rates are
varied by using flexible tubing of
different diameters.
c. Mixing coils: use a 20-turn coil and
a 5-turn coil.
d. Cadmium-copper reduction column: this
U-shaped column is approximately 5 in. long
and 1 - ~\% in wide. Pyrex glass tubing,
4 mm O.D., 2 m I.D., is used to build it.
7.2 Analysis Reagents
All reagents should conform to ACS specifications for
reagent grade materials unless otherwise specified.
7.2.1 Ammonium Chloride. Weigh 20.0 g NH4C1 (ammon-
ium chloride) and place in a 2-liter volu-
metric flask. Add about 1000 ml alkaline
water. (Adjust distilled water pH by adding
29
-------
NH^OH.) Swirl to complete solution. Dilute
to the mark with alkaline water. Add 1.0 ml
Brij-35* with a graduated pi pet. Rinse the
pi pet twice with the solution. Store reagent
at room temperature.
7.2.2 Color Reagent. Weigh .25 g NEDA [n-(naphthyl)
-ethylene-diamine dihydrochloride] and 5.0 g
sulfanilamide and place in a 500 ml volumetric
flask. Add about 50 ml concentrated phosphoric
acid (H3 PO*). Swirl to mix. Dilute to the
mark with distilled water. Mix by inverting
3-4 times. Add .25 ml Brij-35* (wetting agent)
with a 1 ml graduated pi pet. Rinse the pi pet
twice with the solution. Mix well by inverting
10-15 times.
If the solids do not dissolve at once, place
it in a dark area at room temperature. Mix
every 5 to 10 minutes by inversion until the
solids dissolve. Refrigerate in an amber
container.
7.2.3 Stock Nitrate Solution. (1000 yg N03"/ml)
Dry the KNO., (reagent grade or better) over
silica gel or some other drying agent.
Do not heat in an oven1. Weigh exactly 1.6305
g of KNO.J and dissolve in distilled water to
make 1 liter. Add a few drops of chloroform
* Technicon brand name
30
-------
as a preservative. The concentration of this
solution is 1000 yg N03~/m1.
7.2.4 Nitrate Working Standards. Prepare the follow-
ing standards by accurately pipetting the
appropriate amounts of stock nitrate solution
into volumetric flasks. Dilute to volume with
distilled water and mix thoroughly. Prepare
working standards daily.
yg N0~~/ml
II O
A
B
C
D
E
F
G
H
.5
1
2
5
8
10
20
30
e.g., put .5 ml of stock solution in a 100 ml
volumetric flask. Dilute to volume. This
will yield:
.5 ml x 1000 pg M^M __ 5 pg NQ -/ml
100 ml
Prepare a larger volume of one of the standards
to use in every 10th cup of the sample tray.
This will allow the operator to check for
drift and column degradation. Replace the
column if this standard drops more than
3% below its value.
7.2.5 When preparing fresh stock nitrate solution,
run a 5-point calibration curve for the new
and old solutions.
31
-------
7.2.6 Cadmium Filings. Use 99% pure cadmium filings
by filing a cadmium bar. Rinse the filings
once or twice with diethyl ether or 1 N HC1
followed by distilled water. Allow the metal
to air dry. Store in a stoppered bottle.
8. Analysis Procedure
8.1 Filter Preparation. Cut a 3/4" x 8" filter strip from the
exposed glass fiber hi-vol filter with a paper cutter. Place
the folded strip in a 125 ml Erlenmayer flask. Add 35 ml
distilled water and reflux the solution for 30 minutes. Turn
off the heat and cool the flask to room temperature. Rinse
the inside surface of the condenser and adaptor with small
amounts of water from the upper opening of the condenser.
Disconnect the Erlenmayer from the condenser. Vacuum filter
the aqueous extract through a fine sintered glass funnel into
a 50 ml volumetric flask. Wash the remaining filter strip at
least five times with distilled water. Filter through the
same glass filter into the flask. Dilute to 50 ml. Transfer
an aliquot of this solution to a capped culture tube for
future use in the Technicon sample tray.
8.2 Preparation of the Nitrate Reductor Column. Fill the U-tube
with distilled water. Insert a funnel into one end of the U-
tube and partially fill with cadmium filings. Alternate U-
tube ends and repeat this process until column is full of
cadmium. Plug both ends with glass wool.
32
-------
Attach one end of the column to the ammonium chloride
line of the system pump. Run 1 N HC1 through this line
for 1 - 2 minutes. Then run distilled water 1 - 2 minutes,
Dissolve 2 g CuS04'5H20 in distilled water.
Dilute to 100 ml. Obtain 10 ml of this solution and
dilute to 50 ml.
Run the second dilute solution through the column
exactly 1 minute. Rinse again for 1 - 2 minutes with
distilled water. Reverse position of the U-tube and
repeat Cu^SO* solution for 1 minute and distilled
water for 1 - 2 minutes. Remove plugs and squeeze out
cadmium with forced distilled water into a small (50 ml)
beaker. Wash with distilled water and decant small black
particles. (These particles are colloidal copper oxide,
the primary contaminant.) Repeat washings until water
is clear. Air dry or dry in oven until just dry. This
may now be stored for future use.
When ready to use the column fill the U-tube with
distilled water. Add this mossy green copper covered
cadmium until the column is full and most of the water
has been displaced. Plug both ends with glass wool.
Attach a water filled shunt across the U-tube to keep
air from reaching the filings. It may be stored from
day to day or when not in use in this manner.
8.2.1 The reductor column must be clean and have good
flow characteristics for the system to operate
satisfactorily.
33
-------
8.2.2 Pump about TOO ml of distilled water containing
1 ml of stock nitrate solution through the
column for initial activation of the reductor
column.
8.2.3 The reductor column is 99% efficient.
8.3 Use the Technicon Autoanalyzer II for this analysis.
Use a 560 nm interference filter and a 15 mm tubular
flow cell in the colorimeter. Operate the sample
turntable at 40 sample positions per hour with a
^ 1:10 sample to wash ratio. Eight minutes elapse
between sample pickup and appearance of correspond-
ing peak on recorder chart.
8.3.1 Assemble the Technicon Autoanalyzer pump as
shown in Figure 2. See the Technicon II
manual for specific instructions. After
assembling the system, without the reductor
column, attach a shunt (small piece of tubing)
between points A and B (Fig. 2). Place all
pump tubes in their respective solution con-
tainers and check the flows. Put the sample
line in a container of distilled water. Allow
the system to run 5-10 minutes. Check the
debubbler to be sure that no bubbles are
entering the shunt. Attach the nitrate reductor
column at point A first, taking care that no air
bubbles enter the system. Then attach column at
point B. Run the analyzer with a fresh ion
exchange column until a stable baseline is obtained.
34
-------
Pump the chemicals through the system to zero
the instrument. Adjust the range with the
standards to read out as desired on the strip
chart recorder. These standard values will be
used to plot the absorbance vs. concentration curve.
A blank filter strip sample should be inserted
in the analysis system after running the standards.
This will establish the blank absorbance data
required to calculate the final values. Determine
the blank by analyzing 1% of the filters before
use. Cut 3/4" x 8" strips from these filters for
the analysis. Extract the nitrate concentration
from these strips as described in Section 8.1.
This solution will provide the sample to determine
the background levels of NO.," in the blank filters.
8.3.2 After plotting the standard curve and running
the blank sample, the system is ready to analyze
samples. Use a mid-range standard every 10th
sample to check for drift. The baseline will
remain noisy with some tailing throughout the
day. Peak height readings should therefore
always be made by drawing a line connecting
the baseline and measuring at the midpoint.
Samples which exceed the absorbance of the
highest standard of the calibration curve are
diluted until the concentration falls within
the calibration range. A broading of the
colorimeter output with a corresponding loss
35
-------
in peak height usually indicates that the pump
tubing should be replaced. Silicone rubber
tubing is recommended in place of the standard
pump tubing.
8.3.3 Run a color blank on the samples if the extracts
are highly colored or contain suspended particulate.
Remove the NEDA from the coloring reagent. Run
the analyzer with this reagent and with distilled
water in the sample tube. (Other lines are run
normally.) This will establish a baseline for
determining the color absorbance values. These
values are then used to calculate the final
concentration. (Colored samples are not often
found except in extremely polluted areas.)
8.3.4 Run a series of standards including a filter
blank at the end of each day's analysis. Re-
run a random 5-10% of the samples to maintain
internal quality assurance.
8.3.5 Change the glass wool in the ion exchange column
when it gets dirty. The column may be removed
from the system to use the next day if it is
not exhausted. Deterioration can be observed
when the standard sample value decreases.
At the end of an analysis day, replace the
column with a shunt. Place another water-
filled shunt across the column openings to
prevent air contacting column material.
36
-------
8.3.6 Purge this system daily with distilled water.
Do this by placing all chemical lines in water
for 5-10 minutes. All liquid lines should
be left filled with water until the next
sampling time.
8.3.7 Samples should be processed within 2-3 days
after cutting.
8.3.8 Where particulate matter is present, the
solution must be filtered. Filter with a
fine sintered glass filter.
8.3.9 It is critical that the water used in pre-
paring reagents and standards be completely
free of metallic ion contamination. Store
reagents in glass bottles and avoid contact
with air.
8.3.10 Obtain expanded ranges by using the standard
calibration dial on the colorimeter. Refer
to the Technicon II manual to operate the
colorimeter and strip chart recorder.
8.4 Calculations
Plot the absorbance on the y axis and the concentration
on the x axis for the eight points given in Section 7.2.4.
Since Beer's Law is followed, a straight line is obtained
by the equation:
Abs = a x + b
where Abs = absorbance
a = N03~ concentration
the NO ~ concentration (ug/ml) = ^hs " b
X
37
-------
or yg N03~/ml = Absx" b
(Equation 1)
Linearity correlation coefficients are usually greater
than .9995.
Determine the actual tag NO, /ml by subtracting the
blank and color concentrations from the sample con-
centration obtained from Equation 1. (Run standards
before and after each analysis day. Establish the
absorbance vs. concentration curve by averaging these
data.)
Determine nitrate concentration found in the air by:
(yg NO ~/ml) 600
"
yg
area of exposed volume of
,nn filter (9" x 7") liquid (50 ml)
buu area of analyzed strip 3/4" x 7"
600 = 9 x 7 x 50
3/4 x 7
[The actual filter is 8" x 10", but there
is a %" unexposed border around it. Include
the unexposed area when cutting the filter.
This makes a 3/4" x 8" slice.]
Determine the air volume in cubic meters by:
3 Qi + Qf
m3 = -('
where Q^ and Qf are the initial and final flows in
m /min. T is the number of minutes the hi-vol sampler
is run.
38
-------
9. Calibration Apparatus
9.1 The sampler calibration apparatus is that of the hi-volume
sampler method procedure in Section 9.0.
9.2 The analysis calibration apparatus consists of preparing
a series of liquid standards and running these through the
analysis system. These standards are discussed in
Section 7.2.4.
10. Calibration Procedure
10.1 The calibration procedure is that outlined in
Section 10.0 of the hi-vol sampler method.
10.2 The analysis calibration procedure consists of running
a number of known concentrations through the system
and obtaining a calibration curve of the colorimeter
output (absorbance) vs. the input nitrate ion con-
centration. Run a new curve whenever it is necessary
to make new standard solutions. Run curves for both
old and new solutions.
39
-------
REFERENCES
1. "Community Health Air Monitoring Program" (CHAMP), EPA
Contract No. 68-02-0759
2. Morgan, G. B., et al.; "Automated Laboratory Procedures
for the Analysis of Air Pollutants," Presented at
the 59th Annual Meeting APCA, June 20-24, 1966,
San Francisco.
3. "Nitrates Industrial Method," AA II 100-70 W, January
1971, Preliminary Methods, Technicon Autoanalyzer II
Methodology.
4. Armstrong, F. A. J., et al. 1967 Deep Sea Res. 14,
pp. 381-389.
5. Grasshoff, K., Technicon International Congress, June 1969.
6. Federal Water Pollution Control Administration Methods for
Chemical Analysis of Water and Wastes, November 1969.
40
-------
I.e. SUSPENDED SULFATES (SS)
41
-------
I.e. SUSPENDED SULFATES (SS)
Principles and Applicability
1.1 Principles. Suspended sulfates are collected on
the hi-vol filter (Reference Sect. 1). A portion
of this filter is analyzed and concentrations are
obtained utilizing the methyl thymol blue (MTB) method
of sulfate determination.
A strip of the filter is put into a flask with
distilled water and refluxed. The resultant water
soluble sulfate is treated with a reagent containing
equivalent barium chloride and methylthymol blue.
Prevent formation of a barium dye chelate by
maintaining a pH of 2.8. After reaction between the
sulfate and barium ions, an excess of methylthymol blue,
equivalent to the sulfate present, remains. The pH is
increased to 12.4 with sodium hydroxide and the
unreacted barium forms a chelate with the dye. The
excess dye, which is equivalent to the sulfate, is
determined colorimetrically at 460 nm.
1.2 Applicability. This method applies to the analysis
of sulfates collected with the 24-hour hi-volume
sampler.
42
-------
2. Range and Sensitivity
The analysis range is 3.0 to 95.0 pg S07/ml with
the Technicon II linearizer.
3. Interferences
Heavy metal cations interfere by complexing the
methy!thymol blue. These ions are removed by
passing through a cation exchange column.
4. Precision and Accuracy
Precision and accuracy depend upon the region of
the absorbance vs. concentration curve in which
work is being done.
5. Sampling Apparatus
The sampling apparatus is the hi-volume sampler
described in the TSP hi-vol procedure (Refer to
Sect. 1.0).
6. Sampling Procedure
Sampling procedures are identical to those listed
under Section 6.1 in the TSP, hi-volume sampler
document.
43
-------
7. Analysis
7.1 Apparatus
7.1.1 Volumetric flasks, pipets, beakers, and
graduated cylinders to prepare solutions.
Use Class A glassware.
7.1.2 Vacuum Filtering Apparatus: Device which
permits vacuum filtering directly into the
receiver. This consists of a bell jar with a
top opening, a side tabulation and a bottom
plate. The Bunchner funnel passes through
the top opening and is sealed to the bell
jar with a stopper. The bell jar should be
tall enough to contain the polyethylene bottles
used for storing the samples. The vacuum
connection is made using the side tabulation.
The filtering apparatus is shown in Figure 1.
7.1.3 Vacuum Pump: Any device which can maintain a
of at least 64 cm of Hg. Mechanical pumps or
water aspirators may be used.
7.1.4 Polyethylene Bottles: Bottles with a capacity of
60 ml (2 Oz) fitted with polyseal caps.
7.1.5 pH Meter: Capable of measuring pH to nearest
0.1 pH units over a range of 0-14.
44
-------
Buchner Funnel with
Fritted Disc
To Vacuum
Pump
Polyethylene
Bottle
Bell Jar
Baseplate
Figure 1 - Vacuum Filtering Apparatus
45
-------
7.1.6 Glass Bottles (brown). 500 ml glass bottles with
polyseal caps.
7.1.7 Pump Tubing. Flow rates tubing of the capacities
shown in Figure 2. Silicone tubing is recommended
and has a life of up to 6 weeks. Deviations from
these flow rates are acceptable only to the extent
that a proper calibration curve and acceptable
quality control checks are obtained. The use of
silicone rubber tubing in place of the standard
pump tubing is highly recommended. Standard pump
tubing should be replaced every day if used. Other
available tubing has correspondingly longer life
(3 weeks) with silicone rubber tubing having
performed satisfactorily for as long as 5 weeks.
If a plasticized tubing is used, it should be
washed with acetone followed by distilled water
prior to its use.
7.1.8 Erlenmeyer Flask. 125 ml with 24/40 joint.
7.1.9 Condenser. Water jacketed, 300 mm length with
24/40 joints.
7.1.10 Hot Plate. Suitable for sample extraction (7.2.1).
7.1.11 Pyrex Glass Wool.
7.1.12 Plastic Tubing. 10 cm (3.94 in) and 2.3 mm (0.09 in)
I.D. Polyvinylchloride tubing, for ion exchange
column (5.2.1.5).
46
-------
The column consists of a length of glass tubing
7.5 in. long, 2.0 mm inner diameter, and
3.6 outer diameter. The column is then filled
filled with the resin. Keep air out. Place
glass wool plugs at each end to prevent the
resin from escaping. These plugs should not
restrict flow.
It is very important that no air bubbles
enter the ion-exchange column. If air
bubbles become trapped, the column should
be repacked.
f. 15 mm flow cell colorimeter: a colorimeter
of the phototube variety operated with an
auxiliary power supply and amplifier for use
at 460 nm and including a tubular flow cell.
(The interference filters should be checked
before use and at quarterly intervals for
wavelength of maximum transmission.)
g. Recorder: 0-10 mv strip chart recorder.
h. Technicon linearizer: obtains readings
directly proportional to concentration.
49
-------
7.2 Analysis Reagents
7.2.1 Barium Chloride. (.006 m, ACD grade) Dissolve
1.4659 gm BaCl2.2H20 in distilled water and dilute
to 1000 ml in a volumetric flask. Mix well by
inverting 10 to 15 times. Store at room temper-
ature in a screw-top polyethylene container.
7.2.2 Methyl thymol Blue. Weigh 0.1301 gm methylthymol
blue. Add to a clean, dry 500 ml volumetric flask.
(If a dry flask is unavailable, rinse a flask with
about 10 ml alcohol and drain for at least 10
minutes.) Dissolve the dye with 25.0 ml (volumetric
pipet) BaCl2 solution. Add 4.0 ml 1 N HC1 (volu-
metric pipet). Mix by swirling. Carefully add
ethanol until the flask is 2/3 full, making sure
all the dye in the neck of the flask is washed
down. Swirl carefully to mix. Add more ethanol
until the line is reached. Stopper and mix by
inverting ONCE. If necessary, add more ethanol
to bring the level to the mark. Now add 5.0 ml
Brij-35 (Technicon trade name) and rinse the
pipet twice in the dye solution. Stopper and
mix by inverting ONCE. Carefully pour the solution
into a brown storage bottle.
This reagent may be made daily. It should be
stored in a refrigerator when not in use. Do not
keep the reagent more than 3 days.
50
-------
7.2.2 Comment. The ratio of MTB to Ba++ varies because
of the impurities found in different lots of MTB
dye. It may be possible to linearize the absorbance
curve by slightly changing the MTB to BA++ ration.
However, it is presently recommended to use the
absorbance curve directly or a linearizer made
specifically for the Technicon II system.
7.2.3 HC1 (ACS) ( IN). Add about 200 ml distilled
water to a 500 ml graduated cylinder. Add
(volumetric pipet) 25.0 ml concentrated HC1.
Mix by swirling. Dilute with distilled water
to 300 ml. Store at room temperature in a screw-
cap polyethylene bottle.
7.2.4 NaOH (ACS) (0.18N). Dilute 9.0 ml (volumetric)
ION NaOH to 500 ml (volumetric). Mix well. Be
sure the bottle contains at least 300 ml at the
beginning of the run. Also be sure that the end
of the line from the Technicon pump goes down to
the bottom of the bottle.
7.2.5 NaOH (ACS) (ION). Prepare by dissolving 400 g
NaOH pellets in boiled distilled water, cooling,
and diluting to 1 liter with boiled distilled
water. Store at room temperature in a polyethy-
lene container.
7.2.6 Sodium (Tetra) Ethylenediamine Tetraacetate (EDTA)
Cleaning Solution (Technical Grade). Weigh 6.75 g
NH4C1 and 26.9 EDTA, acid form. Add to a 1-liter
-------
volumetric flask. Add about 500 ml water and
swirl to form a suspension. Add 37 ml ION NaOH
and 57 ml concentrated ammonium hydroxide. Mix
and dilute to 1 liter.
7.2.7 Ethanol. 95% U.S.P.
7.2.8 Ammonium Chloride. ACS Reagent Grade.
7.2.9 Concentrated Ammonium Hydroxide. ACS Reagent
Grade, 28-30% NH3-
7.2.10 Sodium Sulfate. ACS Reagent Grade, anhydrous.
7.2.11 Distilled Mater. ACS Reagent Grade, having a
specific conductance of 2 micromhos or less.
7.2.12 Potassium Chloride. ACS Reagent Grade.
7.2.13 Stock Sulfate Solution. Dissolve 1.4789 g sodium
sulfate (Na2S04), previously heated to 105°C for
4 hours and cooled in a dessicator. Dilute to
1000 ml with distilled water. This stock solution
contains 1000 yg SO^/ml. Store in a refrigerator.
Prepare solution monthly and check the new against
the old by running 5-point calibration curves.
7.2.14 Working Standards. Dilute 50.0 ml of stock solution
containing 1000 yg S04~/ml to 500 ml with distilled
water. This intermediate sulfate solution contains
100 ug S0.~/ml. Prepare by pipeting (volumetric
pi pets) appropriate amounts of the stock sulfate
solution into 100 ml volumetric flasks and diluting
to volume with distilled water. These are prepared
52
-------
daily. They may be used up to one week if well
stoppered and in large volumes. Mix well by
stoppering and inverting 10 to 15 times.
7.2.14.1 Prepare a series of working standards
according to the following table:
Working^ Std.
yg S0.=/ml
*T
60
50
40
30
20
10
5
Volume of Std
(to be diluted)
60 ml of 100 yg SO-T/ml
50 ml of 100 " *
40 ml of 100 "
60 ml of 100 "
20 ml of 100 "
10 ml of 100 "
5 ml of 100 "
Final Volume
(dilute with
dist. H20)
100 ml
100 ml
100 ml
200 ml
100 ml
100 ml
100 ml
7.2.14.2 Standards to be used with linearizer:
A. 25 yg S04~/ml
B. 40
C. 55
D. 70
E. 80
F. 90
Larger volumes of 30 yg S0*~/ml standard
or 55 yg SO* /ml are prepared to use
as standards. When using the linearizer,
a non-linearized calibration curve is
first plotted by placing the linearizer
in the direct mode. Using the non-linear
curve, concentrations of standards are
selected which fall at approximately 75%
for each range of the linearizer. For
53
-------
example, a concentration which falls at
15% of scale in the non-linearized mode
should be selected as the standard for
the 0-20% range of the linearizer. These
concentrations as calculated are then
used to set the linearizer as directed
in the linearizer manual.
8. Analysis Procedures
8.1 Filter Preparation. Cut a 3/4 x 8" filter strip from the
center of the exposed glass fiber hi-vol filter with a
paper cutter. Cut the same section from each filter to
maintain uniformity. The use of a template is suggested.
Place the folded strip in a 125 ml Erlenmeyer flask. Add
35 ml distilled water and reflux the solution for 30 min-
utes. Turn off the heat and cool the flask to room temper-
ature. Rinse the inside surface of the condenser and adaptor
with small amounts of water from the upper opening of the
condenser. Disconnect the Erlenmeyer from the condenser.
Vacuum filter the aqueous extract through a fine sintered
glass funnel. Wash the remaining filter at least five
times with distilled water.
Vacuum filter the aqueous extract through a fine sintered
glass funnel into a 50 ml volumetric flask. Wash the re-
maining filter strip at least five times with distilled
water. Filter through the same glass filter into the flask.
54
-------
Dilute to 50 ml. Transfer an aliquot of this solution
to a capped culture tube for future use in the Technicon
sample tray.
8.2 Analyzer Assembly and Use
8.2.1 Perform the sulfate analysis on a Technicon II
Autoanalyzer. Use interference filters of 460 nm
and a 15 mm tubular flow cell in the colorimeter.
Operate the sample turntable at 30 sample positions
per hour with a ^1:3 sample to wash ratio. Eight
minutes elapse between sample pickup and appearance
of corresponding peak on recorder chart.
8.2.2 Assemble system with flows as shown in Figure 2.
Refer to Technicon II manual for specific assembly
instructions.
8.2.3 After assembling the system, attach a shunt (small
piece of tubing) between points A and B (Fig. 2).
Place all pump tubes in their respective solution
containers and check the flows. Put the sample
line in a container of distilled water. Allow the
system to run 5-10 minutes. Check the debubbler
to be sure that no bubbles are entering the shunt.
Attach the ion exchange column at point A first,
taking care that no air bubbles enter the system.
Then attach column at point B. Run the analyzer
with a fresh ion exchange column until a stable
baseline is obtained. This usually requires a
minimum of 2 hours. Mith the sample line in
55
-------
deionized water, pump the chemicals through the
system to zero the instrument. Adjust the range
with the standards to read out as desired on the
strip chart recorder or the linearizer printout.
These standard values will be used to plot the
absorbance vs. concentration curve, or to set the
curve in the linearizer. A blank filter strip
sample should be inserted in the analysis system
after running the standards. This will establish
the blank absorbance data required to calculate the
final values. The blank is determined by analyzing
1% of the filters before use. Cut 3/4" x 8" strips
from these filters for the analysis. Extract the
sulfate concentration from these strips in the
manner described in Section 8.1. This solution
will provide the sample to determine the background
levels of S04~ in the filter.
8.2.4 After plotting the standard curve, the system is
ready to analyze samples. Use a mid-range standard
every 10th sample to check for drift. The baseline
will remain noisy with some tailing throughout the
day. Peak height readings should therefore always
be made by drawing a line connecting the baseline
and measuring at the midpoint. Samples which exceed
the absorbance of the highest standard of the calibra-
tion curve are diluted until the concentration falls
56
-------
within the calibration range. A broadening of the
colorimeter output with a corresponding loss in
peak height usually indicates that the pump tubing
should be replaced. Silicone rubber tubing is
recommended in place of the standard pump tubing.
8.2.5 Run a color blank on the samples if the extracts
are highly colored or contain suspended particulate.
Do this by diconnecting the MTB tube and running
the analyzer without the MTB. Replace the MTB with
ethanol and establish a new zero line with distilled
water in the sample tube. The color absorbance
values from the sample blanks should then be used
in calculating the final concentration.
8.2.6 Run a series of standards including a filter blank
at the end of each day's analysis. Rerun a random
5-10% of the samples to maintain internal quality
assurance.
8.2.7 Change the glass wool in the ion exchange column
when it gets dirty. The column may be removed
from the system to use the next day if it is not
exhausted. Deterioration can be observed when
the standard sample value decreases.
At the end of an analysis day, replace the
column with a shunt. Place another water-filled
shunt across the column openings to prevent air
contacting column material.
57
-------
8.2.8 Purge this system daily with an EDTA solution.
Do this by placing the methyl thymol blue, sample,
and the NaOH lines in water for 2-4 minutes. Then
place them in the EDTA solution for 10 minutes.
Wash system with water for 15 minutes before
shutting down.
All liquid lines should be left filled with water
after the system has been washed. A coating will
slowly develop on the internal parts of the flow
system. When the coating becomes noticeable, the
mixing coils should be cleaned by pumping 1 N
ammonium hydroxide through the system. The rate
at which the coating develops is variable depending
on the nature of the samples being analyzed. A
coating will slowly build up on the flow cell win-
dows which is not removed by the NH»OH wash. This
build-up is indicated by a loss in colorimeter
sensitivity and may be corrected by washing the
cell with 1 N HC1 followed by an acetone and
then a water wash.
8.2.9 Obtain alternate strip recorder ranges by using
the Standard Calibration Dial on the colorimeter.
8.3 Calculations
_ , (yg S0//ml ) 600
yg SO '/m-5 =
*
nT
Determine yg S0.~/ml by subtracting the blank and color
(if present) concentrations from the sample concentration
58
-------
observed from the absorbance curve. (Run standards before
and after each analysis day. Establish the absorbance vs.
concentration curve by averaging these data.)
area of exposed volume of
600 = filter (9" x 7") x liquid (50 ml)
area of analyzed strip 3/4 x 7"
600 = 9 x 7 x 50
3/4x 7
[The actual filter is 8" x 10", but there is a
V unexposed border around it. Include the un-
exposed area when cutting the filter. This
makes a 3/4" x 8" slice.]
Determine the air volume in cubic meters by:
o Q1 = Qf
m3 = ( 1 » f ) T
where Q. and Qf are the initial and final flows
in m /min. T i<
sampler is run.
in m /min. T is the number of minutes the hi-vol
9. Calibration Apparatus
9.1 The sampler calibration apparatus is that of the hi-volume
sampler in Section 9.0 in that procedure.
9.2 The analysis calibration apparatus consists of preparing
a series of liquid standards and running these through the
analysis system. These standards are discussed in
Section 7.2.8.
59
-------
10. Calibration Procedure
10.1 The calibration procedure is that of the hi-volume sampler
as outlined in Section 10.0 in that procedure.
10.2 The analysis calibration procedure consists of running a
number of known concentrations through the system and
obtaining a calibration curve of the colorimeter output
(absorbance) vs. the input sulfate ion concentration.
-------
REFERENCES
1. "Community Health Air Monitoring Program" (CHAMP), EPA Contract
No. 68-02-0759.
2. Lazarus, A. L., et al., "A New Colorimetric Microdetermiation
of Sulfate Ion," Automation in Analytical Chemistry (Vol. 1),
New York: Mediad Corp., 1965. pp. 291-293.
3. Parr, S. W., et al. "Determination of Sulfur by Means of the
Turbidimeter," Industrial Engineering Chemistry Annual Edition,
3:66-67, 1931.
4. "Sulfate in H^O and Waste H-O," Industrial Method 118-71,
preliminary Method, Technicon Autoanalyzer II Methodology,
Technicon Instrument Corp., Tarrytown, N.Y., 10591.
61
-------
II. RESPIRABLE PARTICULATE (RSP)
62
-------
II. RESPIRABLE PARTICULATE (RSP)
1. Principle and Applicability
1.1 Particles moving in an air stream tend to follow their
original straight line motion when streamlines of airflow
are deflected by an obstacle. Using this principle, a
cyclone separator divides the respirable, suspended parti-
culates (RSP) of suspended airborne particles of less than
3.5 mm in diameter from the larger particles found in ambient
air (Figure 1). The air sample is first drawn through the
cyclone where larger particles are removed and discarded by
impaction and settlement. The small particles follow the air
vortex, pass through the top of the cyclone and are captured
on a filter media for weighing and further analysis.
1.2 Mass concentration of the fine fraction of matter found in
ambient air is determined from the weight of samples collected
and the volume of air passed through the train during each
24-hour sampling period. Mass concentration is expressed as
q
micrograms per cubic meter (yg/m ).
2. Range and Sensitivity
2.1 The sampler is operated for 24 hours at a flow rate of 9±.5
liters per minute. A meaningful sample will be obtained if
the ambient air partlculate concentration 1s at least 5 ug/m.
Because of the small collection surface, the low concentration
sampling range is sensitive to weighing procedures.
63
-------
Figure 1 - "LOS ALAMOS" CURVE FOR FINE PARTICULATES
cc
HI
J
Q.
CO
o
UJ co
§
Q UJ
uj z
Z UJ
ui O
DC Z
Z Z
o o
1- 1-
0 O
DC DC
LL U.
100 -
90-
80-
70-
60-
50-
40-
30-
20-
10-
0
^~- X
**
FRACTION OF PARTICLES S
PASSED TO Fl LTER CASSETTE /
/'
x
/ FRACTION OF PARTICLES
/ SEPARATED OUT BY CYCLONE
/
/
X
/
X
/
/
/
v
i i i I i i i i i
3^12 3 4 5 6 7 8 9 10
AERODYNAMIC PARTICLE SIZE AT UNIT DENSITY, MICRONS
64
-------
Filter and sampling weights are determined with an
accurate balance. Weights are made to the nearest
0.01 milligram. Flow rates are measured to the nearest
0.1 liter per minute with a calibrated rotameter. Samp-
ling times are recorded to the nearest minute.
2.2 RSP concentrations found in ambient atmospheres range
3
to highs of over 200 yg/m . Minimum detectable concen-
trations are based on the accuracy of the balance.
3. Interferences
3.1 High humidity or rainfall pulled into the filter may dissolve
the water-soluble portion of the sample.
3.2 The filter does not have water vapor gathering properties.
The particles themselves, however, can be hygroscopic and
introduce errors in weight determinations if samples are
not carefully equilibrated to a fixed, environmentally
controlled humidity and temperature level before weighing.
4. Precision and Accuracy
4.1 The accuracy of samplers measuring the true average con-
centration depends upon the degree of constant air flow
maintained in the samplers and in making weight deter-
minations of collected samples.
4.2 Results of duplicate sampling at the Durham, North Carolina
Ambient Air Station have given a correlation coefficient
of 0.97 for cyclone samplers. At an average mass concen-
3
tration of 115 yg/m of particulate matter in ambient air,
65
-------
the measurement error determined by duplicate sampling
3
averaged ±5 percent; at an average of 39 yg/m the
measurement error averaged 13 percent.
4.3 Start and stop flow rates are measured within 2 percent.
This corresponds to the accuracy of the rotameter.
5. Sampling Apparatus
5.1 Cyclone. A 1.27 cm diameter stainless steel cyclone
collector is used to separate the respirable fraction
of the total suspended particulates. Only the smaller
2
particles are collected on the filter. The others fall
to a cup at the bottom of the separator. This cyclone
sampler is illustrated in Figure 2.
5.2 Cassette. An airtight plastic cassette is used to house
the 37 mm preweighed filter and filter support. This
cassette can be opened by hand to easily change filters.
5.3 Filter and Filter Support. The filter is a 37 mm circular
glass-fiber filter. A porous material is placed on the
back side of the filter for additional support. Other
filter media may be substituted, but all should have a
99+ percent collection efficiency for particles under
3.5 ym diameter.
5.4 Critical Orifice. A limiting orifice will provide a
constant flow of 9(±.5) liters per minute over a range
of vacuums between 50.8 - 66.0 cm Hg (20 - 26 in.) on
the pump gauge.
5.5 Vacuum Pump. This pump must maintain a vacuum of at
least 50.8 cm Hg (20 in.) and a 10.5 liter per minute
flow.
66
-------
Figure 2 - CYCLONE SAMPLER AND SHELTER ASSEMBLY
SHELTER
MAST SUPPORT
AND VACUUM LINE
RSP FILTER CASSETTE
CRITICAL ORIFICE,
9.0 LITER/MIN.
RUBBER
VACUUM HOSE
CONNECTIONS
CYCLONE SEPARATOR
67
-------
5.6 Connections. The vacuum system is connected by 1/4" O.D.
tubing to the base of the cast iron pipe support. The
cassette, cyclone, and orifice are connected with 1/8"
I.D. heavy-walled vacuum hose (Figure 2). All connec-
tions between cassette, cyclone and orifice should be
easily disassembled, but should seal tightly.
5.7 Shelter. The shelter (Figure 2) protects the filter
and cassette from rain and snow.
5.8 Rotameter. The rotameter measures the 9 liters per
minute flow to the nearest .1 liter. A calibration
table is used with the rotameter to determine actual
flows in the field.
6. Sampling Procedure
6.1 To field sample, connect the cyclone in series with a
pre-weighed 37 mm filter and filter pad in the airtight
plastic cassette (Figure 2). The cassette-separator
assembly is attached by rubber tubing to the orifice.
Leave the orifice attached to the mast support arm. Change
it only when it becomes clogged. A vacuum pump moves
ambient air through the train.
6.2 Samples are changed every 24 hours.
6.3 Check the flow at the beginning and end of each sampling
period by replacing the cyclone with the rotameter.
Record the start flow with a clean filter and the stop
flow with a soiled filter.
68
-------
6.4 As with all the manual sampling methods described, fill
the data forms in at the time the sample is changed.
(These data are extremely important to determine daily
pollutant concentrations.)
Data include:
A. Start and stop times in military units (e.g.,
3:45 p.m. = 1545) (T)
B. Start and stop flows in liters per minute
(Sec. 8.6.1., Qi} Qf)
C. Start and stop dates
D. Initial and final weights (Sec. 8.6.2., V^, Wf)
E. Flowmeter number
F. Pump serial number
G. Filter number
H. Orifice number
I. Any conditions which can affect the sample should
be noted in the "Comment" section (e.g., high winds,
local construction, severe rains, etc.)
6.5 The rotameter monitors the flow through each orifice.
This flow must stay in the 8.5 - 9.5 liter per minute
range. Replace any orifice not in this range.
7. Analysis Apparatus
7.1 Maintain the environmentally controlled chamber between
15-35°C and less than 50 percent relative humidity.
7.2 A balance capable of weighing to the nearest .01 milli-
gram, ±.005 mg.
69
-------
8. Analysis Procedure
8.1 Equilibrate all filters in the environmental chamber 24
hours before preweighing. Weigh the filters to the
nearest 0.01 mg.
8.2 Place a filter in a cassette and assign a number to it.
8.3 Send the filter cassette to the field operator.
8.4 When the exposed filter cassette is returned, carefully
remove the filter and equilibrate it in the chamber for
24 hours before its final weighing.
8.5 Record on the data card the initial and final weights.
8.6 Concentrations Determinations, a computer determines
concentrations from the data forms completed by the
field operator and laboratory personnel. Use the
initial and final weights and flows to compute the
RSP concentrations.
8.6.1 Determine volume of air sampled from the
equation
Qi +Qf
V = 1 2 r x T
3
where V = air volume sampled, m
Q. = initial airflow rate, m /min
3
0- = final airflow rate, m /min
T = sampling time, min.
8.6.2 Determine mass concentration of suspended
particulates from the equation
(W. - W-) x 106
S.P.= ! -
70
-------
where S.P. = mass concentration of suspended
3
particulate, yg/m
W.. = initial weight of filter, grams
W,: = final weight of filter, grams
10 = conversion of g to u grams
9. Calibration Apparatus
9.1 Orifice Calibration Apparatus
9.1.1 Mass flowmeter equipped with a transducer
capable of a range of 0 to 10,000 cc/tnin
or 0 to 10 liters/min. (The mass flowmeter
is periodically calibrated with a Brooks
calibrator.)
9.1.2 A vacuum pump must maintain 50.8 cm Hg (20 in.)
to provide a critical flow of 9 liters per minute.
9.1.3 Vacuum tubing
9.1.4 Needle valve
9.1.5 Short sections of heavy rubber vacuum hose.
9.1.6 RSP orifice and tubing connectors.
9.2 Rotameter Calibration Apparatus
9.2.1 Wet test meter (1 liter/revolution) or a mass
flowmeter with digital read-out as in 9.1.1.
9.2.2 Vacuum source capable of at least 50.8 cm Hg
(20 in.)
9.2.3 Vacuum tubing
9.2.4 Needle valve
9.2.5 Rotameter
9.2.6 Ring stand and clamps
9.2.7 Stop watch
9.2.8 Manometer and thermometer
71
-------
10. Calibration Procedures
10.1 Orifice Calibration Procedure
10.1.1 Set up materials as shown in Figure 3, taking care
that 'all connections are secure to prevent air
leakage.
10.1.2 Allow the mass flowmeter 30 minutes warm-up time.
10.1.3 Place an orifice into the train with the arrow
on the orifice pointed toward the vacuum source
or the direction of the airflow.
10.1.4 Record the orifice number, calendar date, and
operator's initials.
10.1.5 Check to make sure the needle valve is closed.
10.1.6 Start up the vacuum source.
10.1.7 Regulate the vacuum to about 20 in. of vacuum.
This prevents over-taxing the pump during cali-
bration and also keeps the orifice at critical
flow.
10.1.8 Open the needle valve slowly, until the mass
flowmeter reading reaches a constant flow.
10.1.9 Record this flow as the critical or calibration
point. The orifice is accepted or rejected at
this point based on the flow. It is under these
critical conditions that the orifice operates
in the field.
10.1.10 The RSP sampling network calls for flows of 9
liters/min. during sampling. The tolerance of
these flows if ±5 liters/min.
72
-------
o
DC
CO
O
LLI
g
LL
QC
O
Q_
CO
or
0)
S-
cr>
LU
O
CC
73
-------
NOTE: The orifice should operate in a constant
"critical flow" region. Filter loading and/or
vacuum changes, however, could change this.
10.2 Rotameter Calibration Procedure
10.2.1 Set up materials shown in Figure 4. Make sure
all connections are tight to prevent leakage.
10.2.2 Mount the rotameter in a vertical position.
10.2.3 Level the wet testmeter by using the bubble level
and the screw legs.
10.2.4 Adjust the water level in the testmeter using
distilled water, by either draining or adding
water. The needle in the glass tube should just
touch the water surface.
NOTE: Steps 10.2.3 - .4 are critical if an accurate
calibration is to be obtained. A mass flowmeter
may be used and steps 10.2.3 - .4 are eliminated.
10.2.5 Prepare data sheet as shown in Figure 5.
10.2.6 Record rotameter number, calendar date, room
temperature, atmospheric pressure (P), and
operator's initials.
10.2.7 Start up the vacuum pump, and adjust the needle
valve until a stable reading is acquired on the
rotameter. Read the center of the ball.
10.2.8 Allow for an equilibration period if the wet
testmeter thermometer is much different from
the room temperature.
74
-------
DC
at
LU
DC
DO
O
QC
LJJ
O
cc
S-
3
o>
A
O EC
oc Mf-
ti
N
II
IU LL
i
OQ
75
-------
Figure 5: Typical data sheet
Rotameter
Setting
30
40
50
60
70
80
90
Vl
9.0 1
9.0 1
9.0 1
Vl
corrected
Water
Temp.
P
Vacuum
t
time
for
each
run
Flow=
v2/t
76
-------
10.2.9 Record the temperature in °C and the manometer
readings in inches of water. Record the start
value for the rotameter.
10.2.10 Start the stopwatch when the wet testmeter hand
crosses a convenient mark.
10.2.11 Allow the wet testmeter to run freely until 9
liters of air have been pulled through.
10.2.12 Stop the watch and record the run time.
10.2.13 Record the rotameter stop value.
10.2.14 Make sure there have been no significant changes
in the temperature or vacuum. (Not more than
VC or .2" of water.)
10.2.15 Repeat steps 10.2.10 through .14 for readings
on the RSP rotameter of 30, 40, 50, 60, 70, 80
and 90.
10.3 Calculation of Calibration Data
10.3.1 Calculate the total volume being pulled through the
wet testmeter according to the calibrating condi-
tions. Use the following formula:
' Pl Vl _ P2 V2
Tl T2
where P-, = corrected pressure during calibration
T-, = water temperature +273°C
V-, = volume = 9 liters.
Conditions where rotameter is calibrated.
PP = Pressure = 760 mm Hg
T2 = Temperature 298.15°K
V« = Volume in liters.
STP conditions.
77
-------
10.3.2. Correct the pressure for water vapor pressure by
taking the temperature readings in °C and referring
to a vapor pressure chart. (One such chart is in
the HANDBOOK OF AIR POLLUTION of the U. S. Dept.
of Health, Education and Welfare.) Subtract this
reading from the barometric pressure to get the
corrected pressure, P-, .
10.3.3 Calculate the actual flow of reach rotameter
reading. Divide actual volume ^K computed in
steps 10.3.1 and .2, by the time taken for each
flow measurement.
10.3.4 Repeat steps 10.3.1, .2, and .3 for each rotameter
calibration point.
10.3.5 A standard_referenced mass flowmeter with a digi-
tal read-out can be used to provide a quicker
method to calibrate the rotameters. A water
vapor pressure correction is unnecessary when
using this mass flowmeter. Therefore, P can
be used directly.
10.4 Plotting the Graph
10.4.1 Plot all points carefully on regular graph paper
(10 x 10 to the inch). See Figure 6.
10.4.2 Obtain a linear regression of these points. From
this regression obtain a chart of rotameter read-
ing vs flow. Increment the flow in 0.02 1/min.
increments. Tape this chart to the side of the
rotameter. The chart is used by the field operator
to obtain Q. and
78
-------
Figure 6 - ROTAMETER CALIBRATION CURVE
33
c
m
Tl
O
m
33
CO
13
m
33
2
C
H
m
ROTAMETER READINGS
-------
REFERENCES
1. Aerosol Technology Committee, American Industrial Hygiene Assoc.,
"Guide for Respirable Mass Sampling," Am. Ind Hyg. Assoc. J_.
31:133 (1970)
2. Burton, R. M., et al., "Development of Fine Particulate Sampling
Methods in Support of CHESS Health Studies," EPA In-house Report.
-------
III. SULFUR DIOXIDE (S09)
81
-------
III. SULFUR DIOXIDE
1 . Principle and Applicability
1.1 A stable dichlorosulfitomercurate complex, formed by absorption
of S0£ from air in a potassium tetrachloromercurate solution,
is reacted with pararosaniline and formaldehyde by controlling
the flow rates of sample and reagents. A pararosaniline
methyl sulfonic acid dye is formed. The absorbance, proportional
to the SCL concentration, is measured colorimetrically and
converted to an electrical signal. The signal is displayed in
either digital or analog form on a readout device.
1.2 The method applies to integrated 24-hour samples of S02 in
ambient air. Collected samples are analyzed by an automated
procedure in a laboratory.
2. Range and Sensitivity
2.1 Concentrations of sulfur dioxide in the range of 25 to 1050
o
yg/m (0.01 to 0.40 ppm) can be measured under the conditions
3
given. Concentrations below 25 yg/m can be measured by
sampling larger volumes of air, but only if the absorption
efficiency of the particular system is first determined.
Higher concentrations can be measured by using smaller gas
samples, a larger collection volume, or a suitable dilution of
the collected sample. Beer's Law is followed through the
analysis range of 0.02 - 1.4 yg SO^/ml .
82
-------
2.2 The lower limit of detection of sample analysis is
p
estimated to be 0.02 yg SO^/ml. This value would
represent a concentration of 4 yg S02/m (0.0015 ppm)
in a 24-hour sample. However, the minimum detectable
concentration is 25 yg S02/ml, unless the measurement
reliability of concentrations less than 25 yg/m can b<
determined by the absorption efficiency at low levels.
3. Interferences
3.1 The effects of the known interferences have been min-
3*
imized or eliminated. Interferences by oxides of
4
nitrogen are eliminated by sulfamic acid, ozone by time-
delay, and heavy metals by EDTA (ethylenediamine-
tetraacetic acid, disodium salt) and phosphoric acid. '
At least 60 yg Fe (III), 10 yg Mn (II), and 10 yg CR (III)
in 10 ml absorbing reagent can be tolerated. No signi-
ficant interference has been found with 10 yg Cu (III)
and 22 yg V (V).
4. Precision. Accuracy, Stability, and Efficiency
4.1 Precision. Estimates of the relative standard deviation
for 24-hour samples at concentrations of 100, 350, and
900 yg S02/m3 (0.037, 0.13, and 0.34 ppm, respectively)
are 4.2, 0.4, and 0.8 percent.
4.2 Accuracy. No data on accuracy are available.
*See Editor's Note
83
-------
*Editor's Note:
Recent unpublished EPA studies by the Environmental Monitoring
Support Laboratory (EMSL) indicate that SOp concentrations in solution
decay with increasing temperatures. Changes range from .9% per day
at 20°C to 73% per day at 50°C.
To eliminate this problem sampling should be done at a constant
temperature of 25°C or less and the exposed sample kept at 5°C until
analyzed.
84
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4.3 Stability. The presence of EDTA enhances the stability
of S02 in solution. The rate of decay is independent
Q
of SCL concentration, but temperature dependent. At
22°C, loss of S02 occurs at the rate of 1% per day.
Samples stored at 5°C (e.g., in a refrigerator) for
30 days show no detectable loss of SCL.
4.4 Sampling Efficiency. Collection efficiency is above
98 percent; efficiency may fall off at concentrations
below 25 yg/m3.9'10
5. Sampling
5.1 Apparatus
5.1.1 Sampling Train. A sampling apparatus diagram
is shown in Figure 1. The apparatus section,
or sampling train, between the glass intake
manifold and the copper vacuum manifold is
generally supported in a "bubbler box,"
Figure 1-a.
5.1.2 Probe. Teflon, polyethylene, or glass tube
with an inverted polypropylene or glass funnel
at the end.
5.1.3 Absorption Tube. Polypropylene tube 164 x
32 mm, equipped with a polypropylene two-port
cap. Do not use rubber stoppers as they cause
high and varying blank values. A restricted
orifice glass tube is used to disperse gas.
The 152 mm tube, 8 mm O.D. - 6 mm I.D., should
85
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same time when this box arrangement is
employed.
5.1.9 Pump. Capable of maintaining the minimum
vacuum and flows required for the 24-hour
sample. A vacuum of 0.7 atmosphere or
greater is necessary.
5.2 Reagents
All reagents should conform to ACS specifications for
reagent grade materials unless otherwise specified.
5.2.1 Sodium Hydroxide. ACS Reagent Grade.
5.2.2 Sodium Arsenite. ACS Reagent Grade.
5.2.3 Absorbing Reagent. Dissolve 4.0 g sodium
hydroxide in distilled water, add 1.0 g of
sodium arsenite and dilute to 1000 ml with
distilled water.
6. Sampling Procedure
6.1 Assemble the sampling apparatus as shown in Figure 1.
Connect components upstream from the absorption tube
with teflon tubing. Connect glass tubing with dry
ball joints or with butt-to-butt joints of tygon,
teflon, or polypropylene. Add exactly 50 ml of absorb-
ing reagent to the calibrated mark on the absorption
tube.
6.2 Insert the flowmeter into the sample line between the
glass manifold and the sample bubbler to measure the flow.
Note this flow and remove the flowmeter from the system.
89
-------
This process is done immediately after inserting a
new unexposed bubbler tube and just before it is taken
off line 24 hours later. Check the system for leaks
if the flow rate before sampling is not between 180 -
3
220 cm /min. Replace the flow control device if
necessary. Start sampling only after obtaining an
initial flow rate in this range.
6.3 Data forms should be filled in when the sample is
changed. These data are extremely important in cal-
culations used tc determine daily pollutant concen-
trations. They include start and stop times in mili-
tary units (e.g., 3:45 pm = 1545), start and stop flows
in appropriate metric units, start and stop dates, as
well as flowmeter number, pump serial number, filter
number, orifice number, etc. Note any uncorrectible
condition such as high winds, local construction (within
1/4 km), severe rains or other conditions that can affect
the sample.
7. Ana1ys i s
7.1 Apparatus
7.1.1 Volumetric flasks, pi pets, beakers to prepare
solutions and standards. Use Class A glassware.
7.1.2 A Technicon II automated analysis system con-
sisting of the components described below, is
used for the analysis. Fig. 2 shows the
arrangement.
90
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91
-------
a. Sampler IV turntable: set for 40 samples/
hour and a 6:1 ratio of sample to wash time.
b. Proportioning pump III: capable of maintain-
ing the flow rates indicated in Fig. 2. Pump
tubing for the proportioning pump II must be
poly (vinyl chloride) or other inert tubing
for sample and reagent. Silicone tubing is
used for air injection.
c. Sampler probe: made of Kel-F, poly (chlo-
rotrifluoroethylene), or glass. Because of
the corrosive properties of the TCM absorbing
reagent, no metal should contact the sample
solution.
d. Flow rates: sample and reagent flow rates are
specified in Fig. 2. The different flow rates
are obtained by selecting pump tubing of the
proper inside diameter. Flow deviations are
acceptable only to the extent that a proper
calibration curve and quality control checks
are maintained.
e. Mixing coils: 20 turn, 2 mm I.D. glass coils.
f. Heating bath: 45°C heated coil, total volume
5.4 ml.
g. Colorimeter and voltage stabilizer: Colori-
meter with proper filters for measurement of
absorbance at 560 nm. Interference filters
should have a spectral bandwidth not greater
92
-------
than 20 nm. The filters should be checked
with an accurate spectrophotometer at least
quarterly to assure maximum transmittance at
the specified wavelength. The colorimeter
contains a flow cell, 15 mm long with an I.D.
of 2 mm.
7.1.3 Readout Device. A mv strip chart recorder or
digital voltmeter of proper range.
7.2 Analysis Reagents
7.2.1 Sulfamic Acid (0.17 percent). Dissolve 1.7 g
of sulfamic acid in distilled water and bring
to mark in 1000 ml volumetric flask. Prepare
fresh daily.
7.2.2 Formaldehyde (0.2 percent). Dilute 5 ml of
formaldehyde solution (36-38 percent) to 1000 ml
with distilled water. Prepare fresh daily.
7.2.3 Pararosaniline Dye (PRA). The dye must have a
wavelength of maximum absorbance at 540 nm when
assayed in 0.1 M sodium acetate-acetic acid
(7.2.3.2).
7.2.3.1 Stock PRA Solution (0.20%). A specially
purified (99-100%) solution of pararo-
saniline is commercially available in
the required 0.20 percent concentration
(Harleco Company, Gibbstown, New Jersey
08027), but must be assayed. Alternatively,
PRA dye may be prepared from the crystalline
93
-------
form, purified according to the procedure
of ScaringeTIi, Saltzman and Frey, and
assayed.
7.2.3.2 PRA assay procedure. One ml of the stock
solution (0.20% is diluted to the mark in
a 100 ml volumetric flask with distilled
water. A 5 ml aliquot of that solution
is then transferred to a 50 ml volumetric
flask. Five ml of 1 M sodium acetate-
acetic acid buffer (7.2.3.4) is added,
and the mixture is then diluted to 50 ml
volume with distilled water. After 1
hour the absorbance is determined at
540 nm with a spectrophotometer. The
assay of the PRA is determined by the
formula
Fn 1 * PRA a^av = _ Absorbance _
Eq.l. ^ PRA assay - Qf
For 1-cm cells and spectral bandwidth of
less than 11 nm, K = 21.3.
*Assume 0.1 gram of dye taken when assaying
the Harleco solution.
7.2.3.3 PRA Working Reagent.
CAUTION: Always use extreme care in hand-
ling concentrated acid. Add it slowly.
Protect eyes from splatters.
To a 200 ml volumetric flask, add 16 ml
stock pararosaniline solution. Add an
additional 0.2 ml stock solution for
94
-------
each percent the stock assays below 100%
as calculated by Equation 1. Then add
25 ml of concentrated (85%) phosphoric
acid and dilute to volume with distilled
water. This reagent is stable for at
least 9 months.
7.2.3.4 Buffer (Acetate-Acetic acid, 1 M). In a
100 ml volumetric flask, dissolve 13.61
grams of sodium acetate trihydrate in
approximately 50 ml of distilled water.
Then add 5.7 ml of glacial acetic acid
and dilute to volume with distilled
water. (This buffer should have a pH
of 4.7.)
7.3 Calibration Standards
7.3.1 Preparation of Sulfite-TCM Standards.
7.3.1.1 Stock Iodine solution (0.1 N). Place
12.7 g iodine, 40 g potassium iodide,
and 25 ml distilled water in a 1000 ml
volumetric flask. Stir until dissolved,
then dilute to volume with distilled
water.
7.3.1.2 Iodine Solution (0.01 N). Transfer 50 ml
of 0.1 N Stock Iodine Solution to a 500 ml
volumetric flask and dilute to mark with
distilled water.
95
-------
7.3.1.3 Starch Indicator Solution. Triturate
0.4 g soluble starch and 0.002 g mercuric
iodide (preservative) with a little
distilled water, and add the paste slowly
to 200 ml boiling distilled water. Con-
tinue boiling until solution is clear,
and transfer to a glass stoppered bottle.
7.3.1.4 Stock Sodium Thiosulfate Solution (0.1 N).
Dissolve 25 g sodium thiosulfate
(Na2S203'5H20) in 500 ml of distilled
water, add 0.1 g sodium carbonate to the
solution, and dilute to 1000 ml with
distilled water. Allow the solution to
stand one day before standardizing. To
standardize, accurately weigh to the
nearest 0.1 mg, 1.5 g primary standard
(or best available grade with an assay
of 99+ percent) potassium iodate pre-
viously dried at 180°C for 3 hours.
Dilute to volume in a 500 ml volumetric
flask. To a 500 ml iodine flask, pipet
50 ml of potassium iodate solution. Add
2 g potassium iodide and 10 ml of 1 N
hydrochloric acid. Stopper the flask,
and after 5 minutes, titrate with stock
sodium thiosulfate solution to a pale
yellow. Add 5 ml of starch indicator
solution and continue the titration until
96
-------
the blue color disappears. Calculate
the normality (Ng) of the stock solution:
" 2: N = -x 2.80
where N = Normality of stock sodium
thiosulfate solution
V = Volume of sodium thiosulfate
required, ml
W = Weight of potassium iodate, grams
2 80 = (100° mg/g) (0-1 dilution factor)
214 g KI03/mole
6 equivalents/mole
7.3.1.5 Sodium Thiosulfate Titrant (^0.01 N).
Pipet 100 ml of the stock sodium thio-
sulfate solution into 1000 ml volumetric
flask and dilute to the mark with freshly
boiled distilled hLO. The normality (N.)
of the sodium thiosulfate titrant is:
Eq. 3: Nt = 0.100 Ng
where Nt = Normality of the sodium
thiosulfate titrant
0.100 = Dilution factor
N = Normality of stock sodium
thiosulfate solution
(from Equation 2).
97
-------
7.3.1.6 Stock Sulfite Solution. Dissolve
sufficient anhydrous Na^SCL or Na2S205
in 1000 ml of recently boiled, cooled
distilled water to give a solution con-
taining approximately 50 yg S02/ml.
The required amount of either compound
can be calculated as follows:
Eq. 4: grams of Na2S03
or
Eq. 5: grams of Na^Og
Note: The assay of the reagent used should
be 0.97 or greater. Have reagents ready to
analyze this solution immediately.
7.3.1.7 Analysis of Stock Sulfite Solution.
The actual concentration of the solution is
determined by adding excess iodine and
back-titrating with standard sodium thio-
sulfate solution. To back-titrate, pipet
50 ml of the 0.01 N iodine into each of
two 500 ml iodine flasks (A and B). To
flask A (blank) add 25 ml distilled water
and to flask B (sample) pipet 25 ml sulfite
solution. Stopper the flasks and allow to
react for 5 minutes. Prepare the working
sulfite-TCM solution (7.3.1.8) at the
same time iodine solution is added to the
flasks. By means of a buret containing
98
-------
standardized 0.01 N sodium thiosulfate,
titrate each solution in turn to a pale
yellow. Then add 5 ml starch solution and
continue the titration until the blue
color disappears. Record the volumes of
sodium thiosulfate used to titrate the
blank (A) and the sample (B).
7.3.1.8 Working Sulfite-TCM Calibration Standard.
Pi pet 20 ml of the standardized sulfite
solution into a 500 ml volumetric flask
and dilute to the mark with 0.04 M TCM.
Calculate the concentration of sulfur
dioxide in the working solution:
(A - B) (Nt) (32,000) 0
Eq. 6: yg S02/ml = ^ x u'
where A = Volume sodium thiosulfate
for blank, ml
B = Volume sodium thiosulfate
for sample, ml
Nt = Normality of sodium thio-
sulfate titrant from Eq. 3
32,000 = Milliequivalent wt. of
S02, yg
25 = Volume standard sulfite
solution, ml
0.04 = Dilution factor
This solution is stable for 30 days if
kept at 5°C (refrigerator). If not kept
at 5°C, prepare daily.
99
-------
7.3.2 Prepare calibration standards by dilution of the
working sulfite-TCM standard (7.3.1.8)
and subsequent dilution of the 1.0 yg S0?/ml
standards as indicated below. Use absorbing reagent
for all dilutions.
Standard
(ug S02/ml)
20
20
20
1.0
1.0
1.0
Volume of
Standard
(ml)
7.0
5.0
2.0
10.0
4.0
2.0
Diluted to
(ml)
100
100
100
100
100
100
Concentration
(yg S02/ml)
1.4
1.0
0.4
0.10
0.04
0.02
8. Analysis Procedures
8.1 Sample Preparation. After collection, if a precipitate is
observed in the sample, remove it by centrifugation.
Bring sample back to 50 ml with distilled water. (This
assumes loss of volume due only to water evaporation.)
Delay analysis for 20 minutes to allow any ozone to
decompose^
8.2 Sample Analysis
8.2.1 Start reagents flowing through the analyzer system.
The flow cell must be free of bubbles during operation.
Refer to manufacturer's instructions for operating
procedures. The sample and reagent flow rates listed
in Fig. 2 are measured values, and are intended as a
guide to maximize sensitivity.
8.2.2 Set the electronic zero by turning the display rotary
switch to the zero position and adjusting the zero
control for zero percent of scale with a screwdriver.
ion
-------
8.2.3 Set the electronic span by turning the display
rotary switch to the full scale position and
adjusting the full scale control with a screwdriver
for 100 percent of scale.
8.2.4 Set the display rotary switch to the normal operation
mode. With unreacted absorbing reagent in the flow
cell, adjust the baseline to zero.
8.2.5 Once a stable baseline is obtained, span the colori-
meter by introducing a 1.0 yg SOp/ml calibration
standard and adjusting the standard calibration control
to 71.4% of recorder full scale. Use the specified
range of 0 to 1.4 yg SOp/ml. Repeat several times to
verify the setting. If the calibration standard con-
centration is not exactly 1.0, the recorder response
should be adjusted proportionately.
8.2.6 Fill the test cups with samples and place on turntable.
One quality control sample, a 1.0 yg SCL/ml calibration
standard (7.3.2) is included after every 10 samples.
Follow this by enough test cups filled with unreacted
absorbing reagent to provide a baseline check. The
quality control sample must produce a response within
±3.9 scale percent of the value indicated by the day's
calibration curve for valid analyses.
Sample analysis, net yg S02/ml, is determined
directly from the calibration curve (8.2.8). Samples
exceeding the highest calibration standard are di-
luted up to 5:1 with absorbing solution until the
101
-------
sample falls within the range. Rerun a randomly
selected 5-10% of the samples for quality assurance.
8.2.7 Introduce the calibration standards at the beginning,
near the middle, and at the end of each day's analyses.
Record the percent response for each peak and sub-
tract the baseline.
8.2.8 Plot net response in percent of full scale for all
three calibrations (y-axis) vs. the corresponding
concentration in yg S02/ml (x-axis). Draw or
compute the straight line best fitting the data to
obtain the calibration curve. Determine a new cal-
ibration curve for each day's analyses.
8.2.9 Maintenance. Clean the apparatus after each use
to prevent contamination of subsequent analyses.
Consult manufacturer's instructions for cleaning
procedures. Alkaline materials should not be used
because of the formation of a precipitate with TCM.
8.2.10 Waste Disposal. Since the absorbing solution con-
tains mercury, waste solution from the analysis should
be treated prior to disposal or shipment for recla-
mation. The following procedure will remove greater
12
than 99% of the mercury from the absorbing solution:
a. To each liter of waste solution, add 10 g sodium
carbonate until neutral and 10 g of granular
zinc or magnesium.
b. Sodium hydroxide may have to be added if a neutral
solution is not obtained with sodium carbonate.
102
-------
c. Stir the solution for 24 hours in a hood.
CAUTION: Hydrogen gas will be released
during this process.
d. After 24 hours, the solid material (mercury
amalgam) will separate. Decant and discard
the supernatant liquid.
e. Quantitatively transfer the solid material
to a convenient container and dry.
8.2.11 Potential Sources of Error. Sulfur dioxide present
in the air surrounding the Technicon analysis sys-
tem can cause errors in the automated analysis.
3
When using the small, 2 cm Technicon IV sample cups,
an error may result from the diffusion of SOp into
the filled sample cup on the turntable. The error
can be minimized by using larger sample cups such
as disposable culture tubes in place of the small
sample cups, by setting the sample probe so that it
nearly touches the bottom of the culture tube, and
by filling the tubes to the top. This technique
increases the time required for the SCL to diffuse
to the point of sampling.
Also, because room air segments the sample stream,
contamination due to SCL could cause a shift in the
baseline and a false increase due to absorption of
S02 into the sample. If such contamination is sus-
pected, purify the air by passing it through a TCM
solution.
103
-------
8.3 Calculations
8.3.1 Calculate volume of air sampled.
F + F
_ _ - _
v " 2
3
where V = Volume of air sampled, m
F, = Measured flow rate before
sampling, cm /min.
Fg * Measured flow rate after
sampling, cm /min.
T = Time of sampling* min.
10 = Conversion of cm to m .
T ro3 = 106 on3
8.3.2 Uncorrected volume. The volume of air sampled
is not corrected to S.T.P. because of uncer-
tainty associated with 24-hour average tempera-
ture and pressure values.
8.3.3 Calculate the concentration of sulfur dioxide
3
as yg S02/m using:
- (ug S09/ml) x 50
yg S0,/nr = - - - x D
* V
where 50 = Volume of absorbing reagent used in
sampling, ml
V = Volume of air sampled, m
D = Dilution factor = 1 if not diluted.
8.3.4 Equation 1 is determined from the standard run
in Sect. 8.2.7.
(yg/ml) S02 = ax + b
The slope (a) and intercept (b) are used to
calculate S02 concentration.
iru
-------
8.3.5 If desired, concentration of sulfur dioxide may be
calculated as ppm SOp using
m S09 = (pg S09/ml3) x 3.82 x 10"4
C. L.
9. Calibration Apparatus
9.1 Sampling
9.1.1 Mass flowmeter equipped with a transducer, capable
of reading a range of 0 to 10,000 cc/min or 0 to
10 liters/min. (should be periodically calibrated
with a Brooks calibrator). A calibrated wet test-
meter may also be used.
9.1.2 Complete bubbler setup as used in actual sampling
in the field.
9.1.3 27 gauge needles, 3/8" long.
9.1.4 Red serum stoppers.
9.1.5 Vacuum pump capable of 5 to 20 liters/min and
maintaining 0.7 atmospheres of vacuum.
9.1.6 Needle adapter used in the bubbler train in
the field.
9.1.7 Vacuum tubing.
9.2 Analysis Calibration Apparatus and Reagents
9.2.1 Stopwatch capable of measuring 0.1 sec.
9.2.2 Graduated cylinder capable of measuring 0.1 cc.
9.2.3 Other apparatus and reagents discussed in
Sections 7.1 and 7.3.
105
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10. Calibration Procedure
10.1 Needle Calibration
10.1.1 Set up materials as in Figure 3.
10.1.2 Use distilled water in place of the sampling
solution used in the field.
10.1.3 Allow 30-minute warmup for the mass
f1owmeter.
10.1.4 Start up the vacuum pump. Adjust the
pressure gauge to 20" Hg of vacuum or
better to keep from overtaxing the pump.
10.1.5 Place the needle in the train with the
needle pointing away from the vacuum
source. Take care not to bend the
needle. Place it directly in the center
of the serum stopper.
10.1.6 Observe the reading on the mass flowmeter.
The flow should be no less than 180 cc/min
or no greater than 220 cc/min. If this is
not the case, discard the needle.
10.1.7 Follow this procedure for all needles to
be checked, screening good needles from
defective needles.
10.2 Analysis Calibrations
10.2.1 Calibrate the pump tubes using the stopwatch
and graduated cylinder.
106
-------
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107
-------
p, _ amount of solution pumped
time solution pumped
10.2.2. The analyzer calibration is discussed in
Sect. 8.2.
108
-------
REFERENCES
1. Scarengelli, F. P., B. E. Saltzman, .and S. A. Frey,
"Spectrophotometric Determination of Atmospheric Sulfur
Dioxide," Anal. Chem. 39, 1709 (1967).
2. Logsdon, 0. J. II and M. J. Carter, "Comparison of Manual
and Automated Analysis Methods for Sulfur Dioxide in
Manually Impinged Ambient Air Samples." EPA-Region V,
1819 West Pershing Road, Chicago, Illinois 60609.
3. Op. Cit., Scaringelli, Saltzman, Frey.
4. Pate, J. B., B. E. Ammons, G. A. Swanson, J. P. Lodge, Jr.,
"Nitrite Interference in Spectrophotometric Determination of
Atmospheric Sulfur Dioxide," Anal. Chem. 37, 942 (1965)
5. Zurlo, N. and A. M. Griffini, "Measurement of the S02
Content of Air in the Presence of Oxides of Nitrogen and
Heavy Metals," Med. Lavoro, 53, 830 (1962).
*> Off- Cit., Scaringelli, Saltzman, Frey.
7. Op. Cit., Zurlo and Griffini.
8. Scaringelli, F. P., L. Elfers, D. Norris, and S. Hochheiser,
"Enhanced Stability of Sulfur Dioxide in Solution," Anal.
Chem. 42, 1818 (1970).
9. Urone, P., J. B. Evans, and C. M. Noyes, "Tracer Techniques
in Sulfur Dioxide Colorimetric and Conductimetric Methods,"
Anal. Chem. 37, 1104 (1965).
10. Bostrom, C. E., "The Absorption of Sulfur Dioxide at Low
Concentrations (pphm) Studies by an Isotopic Tracer Method,"
Intern J. Air Mater Poll. 9, 333 (1965).
11. Lodge, J. P., et al., "The Use of Hypodermic Needles as
Critical Orifices in Air Sampling," J. Air Pollut. Contr.
Assn. 16, 197-200 (1966). ~
12. Thompson, R. J., J_. Air Pollut. Contr. Assn.. 21, 428 (1971).
109
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IV. NITROGEN DIOXIDE BUBBLERS
110
-------
IV. NITROGEN DIOXIDE BUBBLERS (N02)
Automated Sodium Arsenite Method
1. Principle and Applicability
1.1 Nitrogen dioxide is collected by bubbling air through a
sodium hydroxide arsenite solution to form a stable solu-
tion of sodium nitrite. The nitrite ion produced during
sampling is reacted with phosphoric acid, sulfanilamide,
and N-l-(naphthyl)ethylenediamine dihydrochloride to form
an azo dye. The amount od dye produced is proportional
to the nitrogen dioxide concentration. This dye is
measured colorimetrically and the concentration is obtained
from these measurements.
1.2 The method applies to 24-hour field samples and their
laboratory analysis.
2. Range and Sensitivity
2.1 The analysis range is .01 to 1.4 yg NOp'/ml. Beer's Law
is followed through this range. The range of the method
o p
is 20 to 750 yg/m (0.01 to 0.4 ppm) nitrogen dioxide.
This range requires 50 ml absorbing reagent and a sampling
o
rate of 200 cm /min. for 24 hours. The method is 82-87%
efficient.
2.2 Minimum detectable limits have not been established for
the Technicon II analysis.
Ill
-------
3
3. Interferences
4
3.1 Nitric oxide is a positive interferent. Carbon dioxide
is a negative interferent. These interferences were
combined with ambient concentrations of NCu. At varying
ambient levels, this method has an average positive bias
of 9.9 yg N02/m . The 95% confidence interval for this
bias is 7.5 to 12.2 yg N02/m3.
3.2 Sulfur dioxide interferences are eliminated by converting
it to sulfate ion with hydrogen perioxide before analysis.
4. Precision, Accuracy and Stability
4,1 The relative standard deviations for sampling N02 concen-
o
trations of 78, 105 and 329 yg/m are 3, 4 and 2%.
4.2 Accuracy data is not available.
4.3 Collected samples are stable for at least 6 weeks.
5. Sampling
5.1 Apparatus
5.1.1 Sampling Train. A sampling apparatus diagram is
shown in Figure 1. The apparatus section, or
sampling train, between the glass intake manifold
and the copper vacuum manifold is generally sup-
ported in a "bubbler box," Figure 1-a.
5.1.3 Absorption Tube. Polypropylene tube 164 x 32 mm,
equipped with a polypropylene two-port cap. Dp_
not use rubber stoppers as they cause high and
112
-------
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113
-------
Figure 1-a - BUBBLER BOX
TO SAMPLE
PROBE
TO VACUUM
114
-------
varying blank values. A restricted orifice glass
tube is used to disperse gas. The 152 mm tube,
8 mm 0. D. - 6 mm I.D., should have the end drawn
to 0.3 - 0.8 mm I.D. Position the tube to allow
a 6 mm clearance from the absorber bottom.
5.1.4 Moisture Trap. Polypropylene tube equipped with
two-port cap. The entrance port of the cap is fitted
with tubing that extends to the bottom of the trap.
Loosely pack the unit with glass wool to prevent
moisture entrainment.
5.1.5 Membrane Filter. Porosity of 0.8 - 2.0 microns.
Used to protect flow control device from particulate
matter and moisture. Change the membrane filter after
10 samples.
5.1.6 Flow Control Device. Any device capable of maintaining
a constant flow (±2% for 24 hours) through the sampling
3
solution between 180-220 cm /min. A typical flow
control device is a 27-gauge 3/8" hypodermic needle.
5.1.7 Flowmeter. Used to check the flows at the beginning
and end of a 24-hour sample. Must be capable of
3
measuring 180-220 cm /min to within 5%.
5.1.8 Bubbler Box. Designed to hold the above apparatus,
the box contains a glass inlet and copper exhaust
manifold, each with six sampling ports.
Place a liquid trap on the common exhaust vacuum
line to prevent pump contamination.
Other bubbler samplers may be used at the same
time when this box arrangement is employed.
115
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5.1.9 Pump. Capable of maintaining the minimum vacuum
and flows required for the 24-hour sample. A
vacuum of 0.7 atmosphere or greater is necessary.
5.2 Reagents
/»
5.2.1 Sodium Hydroxide. ACS Reagent Grade.
5.2.2 Sodium Arsenite. ACS Reagent Grade.
5.2.3 Absorbing Reagent. Dissolve 4.0 g sodium hydroxide
in distilled water, add 1.0 g of sodium arsenite
and dilute to 1000 ml with distilled water.
6. Sampling Procedure
6.1 Assemble the sampling apparatus as shown in Figure 1.
Connect components upstream from the absorption tube with
teflon tubing. Connect glass tubing with dry ball joints,
or with butt-to-butt joints of tygon, teflon, or polypro-
pylene. Add exactly 50 ml of absorbing reagent to the
calibrated mark on the absorption tube.
6.2 Insert the flowmeter into the sample line between the glass
manifold and the sample bubbler to measure the flow. Note
this flow and remove the flowmeter from the system. This
process is done immediately after inserting a new unexposed
bubbler tube and just before it is taken off line 24 hours
later.
Check the system for leaks if the flow rate before sampling
is not between 180-220 cm /min. Replace the flow control
device if necessary. Start sampling only after obtaining an
initial flow rate in this range.
116
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6.3 Data forms should be filled in when the sample is changed.
These data are extremely important in calculations used
to determine daily pollutant concentrations. They include
start and stop times in military units (e.g., 3:45 p.m. =
1545), start and stop flows in appropriate metric units,
start and stop dates, as well as flowmeter number, pump
serial number, filter number, orifice number, etc. Note
any uncorrectible condition such as high winds, local con-
struction (within 1/4 km), severe rains or other conditions
that can affect the sample.
7. Analysis
7.1 Apparatus
7.1.1 Volumetric flasks, pipets, and beakers to prepare
standards. Use Class A glassware.
7.1.2 Instrument. Technicon Autoanalyzer II as listed
below:
a. Sample turntable with variable sample rate
and variable sample to wash ratio.
b. Proportioning pump: flow rates are varied
using flexible tubing of varying diameters.
c. Mixing coils: use 3 (20 turn) standard
mixing coils.
d. 40 ft. time delay coil.
e. 15 mm flow cell colorimeter: a phototube
colorimeter operated at 558 nm with an auxil-
iary power supply, amplifier, and a tubular
117
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flow cell. (The interference filters should
be checked before use and at quarterly intervals
for wavelength of maximum transmission.)
f. Recorder: 10 mv strip chart recorder.
7.1.3 Flows in the automated system may be other than
those indicated by Figure 2, but should give
corresponding results to the manual method of
analysis.
7.2 Analysis Reagents
7.2.1 Sulfanilamide. Melting point, 165-167°C.
7.2.2 N-(l-Naphthyl)-ethylenediamine dihydrochloride
(NEDA). Best grade available.
7.2.3 Hydrogen Peroxide. ACS Reagent Grade, 30%.
7.2.4 Sodium Nitrite. Assay of 97% NaNOp or greater.
7.2.5 Phosphoric Acid. ACS Reagent Grade, 85%.
7.2.6 Sulfanilamide Solution. Dissolve 20 g sulfanila-
mide in 700 ml distilled water. Add, with mixing,
100 ml concentrated phosphoric acid and dilute to
1000 ml. This refrigerated solution is stable for
one month.
7.2.7 NEDA Solution. Dissolve 0.5 g of NEDA in 500 ml
of distilled water. Refrigerated and protected
from light, this solution is stable for one month.
7.2.8 Hydrogen Perioxide Solution. Dilute 0.2 ml of 30%
hydrogen peroxide to 250 ml with distilled water.
This solution, protected from light and refrigerated,
can be used for one month.
118
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7.2.9 Standard Nitrite Solution. Dissolve sufficient
dessicated sodium nitrite and dilute with distilled
water to 1000 ml to make a solution containing
1000 yg N02~/ml. The amount of NaNOp to use is
calculated as follows:
where G = Amount of NaN02 grams
1.500 = Gravimetric factor in converting
N02 into NaN02
A = Assay, percent.
Store this solution in the refrigerator.
7.2.10 Working Standards. Dilute 10 ml of the standard
nitrite solution to 500 ml with absorbing reagent.
This intermediate stock solution contains 20.0 yg
N02"/ml . Using this intermediate solution and
absorbing reagent as the dilutent, prepare the
following set of working standards:
Working Standard Volume of Inter- Final Volume
A -/mi\ mediate Standard
02 /m1) (To be diluted) _
1.4 7.0 ml 100
1.2 6.0 ml 100
1.0 10.0 ml 200
0.8 4.0 ml 100
0.5 5.0 ml 200
0.2 5.0 ml 500
0.1 10.0 ml of 1 yg N09"/ml 100
0.05 5.0 ml of 1 " * 100
0.01 2.0 ml of 1 " 200
The .5 yg N02~/ml standard is run every tenth sample to
check the stability of the analytical procedure.
120
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8. Analysis Procedure
8.1 Sample Preparation
8.1.1 Replace water lost by evaporation during sampling
by adding distilled water up to the calibration
mark on the absorption tube. Samples with an
absorbance greater than 1.0 must be reanalyzed
after diluting an aliquot (less than 10 ml) of
the collected sample with unexposed absorbing
reagent.
8.1.2 A problem arises when using the 8.5 ml plastic
cups in the sampling tray. The sample will de-
teriorate with time. The exact mechanism is as
yet unknown. Run the samples so that the liquid
does not remain in these cups for more than 30
minutes.
8.2 Analyzer Assembly and Use
8.2.1 The autoanalyzer is employed for this analysis.
Interference filters of 558 my and a 15 mm tubular
flow cell are used in the colorimeter. The sampler
turntable is operated at 40 sample positions per
hour with a 1:2 sample to wash time ratio. Eight
minutes elapse between sample pickup and appearance
of the corresponding peak on the recorder chart.
8.2.2 Assemble system with flows as shown in Fig. 2.
Refer to Technicon II manual for specific assembly
instructions.
121
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8.2.3 After assembling the system, place all pump tubes
in their respective solution containers and check
the flows. Put the sample line in a container of
distilled water. Allow the system to run 5-10
minutes. Check the debubbler to be sure that no
bubbles are entering the colorimeter.
Run the analyzer until a stable baseline is
obtained. Place the sample line in a container
of unreacted absorbing reagent and pump the
chemicals through the system to zero the instru-
ment. Adjust the range with the standards to read
out as desired on the strip chart recorder.
After running these standards and a blank of
unreacted absorbing solution, plot the absorbance
vs yg N0p~/ml. The system follows Beer's Law.
A straight line passing through the origin should
be obtained. The final curve is prepared for each
batch of samples by averaging 3 sets of standards
(one set at the beginning, one mid-way through the
analysis, and one at the end). The .500 yg NO^'/ml
standard is run every tenth sample to check the
stability of the analytical procedure.
8.2.4 After plotting the standard curve, the system is
ready to analyze samples. Peak height readings
should be made by drawing a line connecting the
baseline and measuring at the midpoint. Samples
which exceed the absorbance of the highest standard
122
-------
of the calibration curve are diluted until the
concentration falls within the calibration range.
A broadening of the colorimeter output with a
corresponding loss in peak height usually indicates
that the pump tubing should be replaced. Silicone
rubber tubing is recommended in place of the stan-
dard pump tubing.
8.2.5 Rerun a random 5-10% of the samples to maintain
internal quality assurance.
8.2.6 Purge this system daily with distilled water.
Place all the reagent tubes in the water and pump
for 15-30 minutes. Leave distilled water in
the system until the next run.
8.2.7 Obtain alternate strip chart recorder ranges by
using the Standard Calibration Dial on the
colorimeter.
8.3 Calculations
8.3.1 Calculate volume of air sampled.
Fi + F? fi
V = ! ?- x T x 10'6
2
3
where V = Volume of air sampled, m
F, = Measured flow rate before sampling,
3. .
cm /mm.
Fp = Measured flow rate after sampling,
cm /min.
T = Time of sampling, min.
fi "3 ^
10" = Conversion of cm to m .
1 m3 = 106 cm3
123
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8.3.2 Uncorrected Volume. The volume of air sampled is
not corrected to S.T.P. because of uncertainty
associated with 24-hour average temperature and
pressure values.
8.3.3 Calculate the concentration of nitrogen dioxide as
3
pg NOp/m using:
3 N02~/ml) x 50
pg N02/m = - v x 0.82 -
where 50 = Volume of absorbing reagent used in sampling, ml
3
V = Volume of air sampled, m
0.82 = Collection efficiency.
>
8.3.4 Equation 1 is determined from the standards run
in Section 8.2.3
(1) pg N02"/ml = ax + b
The slope (2) and intercept (b) are used to calculate
N02~ concentration.
The final curve is prepared for each batch of
samples by averaging 3 sets of standards (one set
at the beginning, one set mid-way through the
analysis, and one at the end).
8.3.5 If desired, concentration of nitrogen dioxide may
be calculated as ppm N02 using
ppm N02 = (pg N02/m3) x 5.32 x 10"4
124
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9. Calibration Apparatus
9.1 Sampling
9.1.1 Mass flowmeter equipped with a transducer capable
of reading a range of 0 to 10,000 cc/min or 0 to 10
liters/min (should be periodically calibrated with a
Brooks calibrator). A calibrated wet testmeter may
also be used.
9.1.2 Complete bubbler setup as used in actual sampling
in the field.
9.1.3 27 gauge needles, 3/8" long.
9.1.4 Red serum stoppers.
9.1.5 Vacuum pump capable of 5 to 20 liters/min and main-
taining 0.7 atmospheres of vacuum.
9.1.6 Needle adapter used in the bubbler train in the
field.
9.1.7 Vacuum tubing.
9.2 Analysis Calibration Apparatus and Reagents
9.2.1 Stopwatch capable of measuring 0.1 sec.
9.2.2 Graduated cylinder capable of measuring 0.1 cc.
9.2.3 Other apparatus and reagents discussed in
Sections 7.1 and 7.2.10.
10. Calibration Procedure
10.1 Needle Calibration
10.1.1 Set up materials as in Figure 3.
10.1.2 Use distilled water in place of the sampling
solution used in the field.
125
-------
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10.1.3 Allow 30-minute warmup for the mass flowmeter.
10.1.4 Start up the vacuum pump. Adjust the pressure
gauge to 20" Hg of vacuum or better to keep from
overtaxing the pump.
10.1.5 Place the needle in the train with the needle
pointing away from the vacuum source. Take care
not to bend the needle. Place it directly in the
center of the serum stopper.
10.1.6 Observe the reading on the mass flowmeter. The
flow should be no less than 180 cc/min or no greater
than 220 cc/min. If this is not the case, discard
the needle.
10.1.7 Follow this procedure for all needles to be checked,
screening good needles from defective needles.
10.2 Analysis Calibrations
10.2.1 Calibrate the pump tubes using the stopwatch and
graduated cylinder.
Flow - amou,nt °f solution pumped
time solution pumped
10.2.2 The analyzer calibration is discussed in
Section 8.2.3.
127
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REFERENCES
1. Christie, A. A., et al. "Field Methods for the Determination
of Nitrogen Dioxide in Air," Analyst 95. 519-524 (1970).
2. Ibid.
3. Beard, M. E., et al. "An Evaluation of the Effects of NO, C02
and Sampling Flow Rate on the Arsenite Procedure for Measurement
of N02 in Ambient Air," Preliminary Draft.
4. Merryman, E. L., et al. "Effects of NO C02, DL, HLO and Sodium
Arsenite on N02 Analysis," Presented at the Second Conference
on Natural Gas Research and Technology in Atlanta, Ga., on
June 5, 1972.
5. Jacobs, M. B. and S. Hochheiser, "Continuous Sampling and Ultra-
microdetermination of Nitrogen Dioxide in Air," Anal. Chem. 30,
426, (1958).
6. Lodge, J. P., et al. "The Use of Hypodermic Needles as Critical
Orifices in Air Sampling," J.A.P.C.A., 16, 197-200 (1966).
7. "Community Health Air Monitoring Program (CHAMP)", EPA Contract
No. 68-02-0759.
128
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CHESS AIR MONITORING SHELTER
Electrical
Mast '
Hi Vo1ume
A i r Samp ling Unit
Gas
Bubbler
Probe
RSP
Samp 1e r
Shelter specs: V x 3' x 2'
Mast approximately 12' above g.ound
129
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APPENDIX
CHESS MONITORING SHELTER
The previously described CHESS sampling apparatus was centralized
in a small aluminum shelter. This 4x3x2 foot prefabricated
shelter was designed to be constructed on site. They were mounted
on 3 ft. aluminum legs which could be bolted to aluminum angles
driven into the ground for extra support. The shelters were painted
white to provide for cooler summer operation. Locks were provided
for the stuctures.
Attached to the shelter exterior were the hi-volume sampler
shelter, the RSP sampling probe, the gas bubbler sampling probe and
a 12-14 ft. electrical mast. The hi-volume sampler shelter was
attached to the CHESS shelter with the air inlet approximately 6 feet
above the ground. The inlet to the gas sampling probe and the RSP
sampler probe was mounted approximately 3 feet above the roof of the
CHESS shelter. The electrical mast was placed approximately 2-3 feet
below ground for maximum support, in concrete if necessary. Housed
in the shelter were the bubbler box, the vacuum pump, the heater and a
temperature controlled exhaust fan. The fan and heater, the hi-volume
sampler motor, and the vacuum pump were attached to separate 15 ampere-
110 volt AC circuits.
The vacuum pump maintained the siample flows for the bubbler box
and the RSP sampler. A spare pump was frequently maintained in the
shelter.
130
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1 REPORT NO.
EPA-600/1 -76-011
4. TITLE AND SUBTITLE
Community Health Environmental Surveillance Studies
(CHESS) Air Pollution Morn tori ng Handbook;
Manual Methods
3. RECIPIENT'S ACCESSIOf*NO.
5. REPORT DATE
January 1976
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
William F. Barnard
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Exposure Assessment Branch
Population Studies Division
Health Effects Research. Laboratory
10. PROGRAM ELEMENT NO.
1AA6Q1
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
Health Effects Research Laboratory
Office of Research & Development
U.S. Environmental Protection Agency
Research Triangle Park, N.C. 27711
13. TYPE OF REPORT AND PERIOD COVERED
14. SPONSORING AGENCY CODE
EPA-QRD
15. SUPPLEMENTARY NOTES
16. ABSTRACT
This document is a methods manual handbook for the Community Health
Environmental Surveillance Studies program. It covers Total Suspended
Particulates (TSP) , Total Suspended Nitrates (TSM) , Total Suspended Sulfates
(TSS), Respirable Suspended Particulate (RSP), Sulfur Dioxide, and Nitrogen
Dioxide. This manual is to be used as a reference publication,
17.
K£Y WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b. IDENTIFIERS/OPEN ENDED TERMS
C. COSATI Field/GlOUp
Air Pollution
Environmental Surveys
Toxicology
Monitors
Community Health. Environ
mental Surveillance
Studies
CHESS
Health Effects Survey
14 B
06 F
18 DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (This Report)
UNCLASSIFIED
21 NO. OF PAGES
138
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UNCLASSIFIED
22 PRICE
EPA Form 2220-1 (9-73)
131
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