Pt. 50, App. A–2 40 CFR Ch.

I (7–1–14 Edition)

[75 FR 35593, June 22, 2010] TCM solution to form a stable

monochlorosulfonatomercurate(3) complex.
APPENDIX A–2 TO PART 50—REFERENCE Once formed, this complex resists air oxida-
METHOD FOR THE DETERMINATION OF tion(4, 5) and is stable in the presence of
SULFUR DIOXIDE IN THE ATMOS- strong oxidants such as ozone and oxides of
PHERE (PARAROSANILINE METHOD) nitrogen. During subsequent analysis, the
complex is reacted with acid-bleached
1.0 Applicability. pararosaniline dye and formaldehyde to form
1.1 This method provides a measurement of an intensely colored pararosaniline methyl
the concentration of sulfur dioxide (SO2) in sulfonic acid.
ambient air for determining compliance with (6) The optical density of this species is de-
the primary and secondary national ambient termined spectrophotometrically at 548 nm
air quality standards for sulfur oxides (sulfur and is directly related to the amount of SO2
dioxide) as specified in § 50.4 and § 50.5 of this collected. The total volume of air sampled,
chapter. The method is applicable to the corrected to EPA reference conditions (25 °C,
measurement of ambient SO2 concentrations 760 mm Hg [101 kPa]), is determined from the
using sampling periods ranging from 30 min- measured flow rate and the sampling time.
utes to 24 hours. Additional quality assur-
The concentration of SO2 in the ambient air
ance procedures and guidance are provided in
is computed and expressed in micrograms per
part 58, appendixes A and B, of this chapter
and in references 1 and 2. standard cubic meter (μg/std m3).
2.0 Principle. 3.0 Range.
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2.1 A measured volume of air is bubbled 3.1 The lower limit of detection of SO2 in 10
through a solution of 0.04 M potassium mL of TCM is 0.75 μg (based on collaborative
tetrachloromercurate (TCM). The SO2
present in the air stream reacts with the

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 Environmental Protection Agency Pt. 50, App. A–2
test results).(7) This represents a concentra- 6.0 Stability.
tion of 25 μg SO2/m3 (0.01 ppm) in an air sam- 6.1 By sampling in a controlled tempera-
ple of 30 standard liters (short-term sam- ture environment of 15° ±10 °C, greater than
pling) and a concentration of 13 μg SO2/m3 98.9 percent of the SO2–TCM complex is re-
(0.005 ppm) in an air sample of 288 standard tained at the completion of sampling. (15) If
liters (long-term sampling). Concentrations kept at 5 °C following the completion of sam-
less than 25 μg SO2/m3 can be measured by pling, the collected sample has been found to
sampling larger volumes of ambient air; be stable for up to 30 days. (10) The presence
however, the collection efficiency falls off of EDTA enhances the stability of SO2 in the
rapidly at low concentrations.(8, 9) Beer’s TCM solution and the rate of decay is inde-
law is adhered to up to 34 μg of SO2 in 25 mL pendent of the concentration of SO2. (16)
of final solution. This upper limit of the 7.0 Apparatus.
analysis range represents a concentration of 7.1 Sampling.
1,130 μg SO2/m3 (0.43 ppm) in an air sample of 7.1.1 Sample probe: A sample probe meeting
30 standard liters and a concentration of 590 the requirements of section 7 of 40 CFR part
μg SO2/m3 (0.23 ppm) in an air sample of 288 58, appendix E (Teflon ® or glass with resi-
standard liters. Higher concentrations can be dence time less than 20 sec.) is used to trans-
measured by collecting a smaller volume of port ambient air to the sampling train loca-
air, by increasing the volume of absorbing tion. The end of the probe should be designed
solution, or by diluting a suitable portion of or oriented to preclude the sampling of pre-
the collected sample with absorbing solution cipitation, large particles, etc. A suitable
prior to analysis. probe can be constructed from Teflon ® tub-
4.0 Interferences. ing connected to an inverted funnel.
4.1 The effects of the principal potential 7.1.2 Absorber—short-term sampling: An all
interferences have been minimized or elimi- glass midget impinger having a solution ca-
nated in the following manner: Nitrogen ox- pacity of 30 mL and a stem clearance of 4 ±1
ides by the addition of sulfamic acid,(10, 11) mm from the bottom of the vessel is used for
sampling periods of 30 minutes and 1 hour (or
heavy metals by the addition of ethylene-
any period considerably less than 24 hours).
diamine tetracetic acid disodium salt
Such an impinger is shown in Figure 1. These
(EDTA) and phosphoric acid,(10, 12) and
impingers are commercially available from
ozone by time delay.(10) Up to 60 μg Fe (III),
distributors such as Ace Glass, Incorporated.
22 μg V (V), 10 μg Cu (II), 10 μg Mn (II), and
7.1.3 Absorber—24-hour sampling: A poly-
10 μg Cr (III) in 10 mL absorbing reagent can
propylene tube 32 mm in diameter and 164
be tolerated in the procedure.(10) No signifi-
mm long (available from Bel Art Products,
cant interference has been encountered with
Pequammock, NJ) is used as the absorber.
2.3 μg NH3.(13) The cap of the absorber must be a poly-
5.0 Precision and Accuracy. propylene cap with two ports (rubber stop-
5.1 The precision of the analysis is 4.6 per- pers are unacceptable because the absorbing
cent (at the 95 percent confidence level) reagent can react with the stopper to yield
based on the analysis of standard sulfite erroneously high SO2 concentrations). A
samples.(10) glass impinger stem, 6 mm in diameter and
5.2 Collaborative test results (14) based on 158 mm long, is inserted into one port of the
the analysis of synthetic test atmospheres absorber cap. The tip of the stem is tapered
(SO2 in scrubbed air) using the 24-hour sam- to a small diameter orifice (0.4 ±0.1 mm) such
pling procedure and the sulfite-TCM calibra- that a No. 79 jeweler’s drill bit will pass
tion procedure show that: through the opening but a No. 78 drill bit
• The replication error varies linearly with will not. Clearance from the bottom of the
concentration from ±2.5 μg/m3 at con- absorber to the tip of the stem must be 6 ±2
centrations of 100 μg/m3 to ±7 μg/m3 at con- mm. Glass stems can be fabricated by any
centrations of 400 μg/m3. reputable glass blower or can be obtained
• The day-to-day variability within an indi- from a scientific supply firm. Upon receipt,
vidual laboratory (repeatability) varies the orifice test should be performed to verify
linearly with concentration from ±18.1 μg/ the orifice size. The 50 mL volume level
m3 at levels of 100 μg/m3 to ±50.9 μg/m3 at should be permanently marked on the ab-
levels of 400 μg/m3. sorber. The assembled absorber is shown in
• The day-to-day variability between two or Figure 2.
more laboratories (reproducibility) varies 7.1.4 Moisture trap: A moisture trap con-
linearly with concentration from ±36.9 μg/ structed of a glass trap as shown in Figure 1
m3 at levels of 100 μg/m3 to ±103.5 μ g/m3 at or a polypropylene tube as shown in Figure
levels of 400 μg/m3. 2 is placed between the absorber tube and
• The method has a concentration-dependent flow control device to prevent entrained liq-
wreier-aviles on DSK5TPTVN1PROD with CFR

bias, which becomes significant at the 95 uid from reaching the flow control device.
percent confidence level at the high con- The tube is packed with indicating silica gel
centration level. Observed values tend to as shown in Figure 2. Glass wool may be sub-
be lower than the expected SO2 concentra- stituted for silica gel when collecting short-
tion level. term samples (1 hour or less) as shown in

19

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 Pt. 50, App. A–2 40 CFR Ch. I (7–1–14 Edition)
Figure 1, or for long term (24 hour) samples during use. Heat-shrink material as shown in
if flow changes are not routinely encoun- Figure 2 can be used to retain the cap seals
tered. if there is any chance of the caps coming
7.1.5 Cap seals: The absorber and moisture loose during sampling, shipment, or storage.
trap caps must seal securely to prevent leaks
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 Environmental Protection Agency Pt. 50, App. A–2
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 Pt. 50, App. A–2 40 CFR Ch. I (7–1–14 Edition)
7.1.6 Flow control device: A calibrated ro- meter is also recommended to determine the
tameter and needle valve combination capa- duration of the sampling period.
ble of maintaining and measuring air flow to 7.2 Shipping.
within ±2 percent is suitable for short-term 7.2.1 Shipping container: A shipping con-
sampling but may not be used for long-term tainer that can maintain a temperature of 5°
sampling. A critical orifice can be used for ±5 °C is used for transporting the sample
regulating flow rate for both long-term and from the collection site to the analytical
short-term sampling. A 22-gauge hypodermic laboratory. Ice coolers or refrigerated ship-
needle 25 mm long may be used as a critical ping containers have been found to be satis-
orifice to yield a flow rate of approximately factory. The use of eutectic cold packs in-
1 L/min for a 30-minute sampling period. stead of ice will give a more stable tempera-
When sampling for 1 hour, a 23-gauge hypo- ture control. Such equipment is available
dermic needle 16 mm in length will provide a from Cole-Parmer Company, 7425 North Oak
flow rate of approximately 0.5 L/min. Flow Park Avenue, Chicago, IL 60648.
control for a 24-hour sample may be provided
7.3 Analysis.
by a 27-gauge hypodermic needle critical ori-
fice that is 9.5 mm in length. The flow rate 7.3.1 Spectrophotometer: A spectrophotom-
should be in the range of 0.18 to 0.22 L/min. eter suitable for measurement of
7.1.7 Flow measurement device: Device cali- absorbances at 548 nm with an effective spec-
brated as specified in 9.4.1 and used to meas- tral bandwidth of less than 15 nm is required
ure sample flow rate at the monitoring site. for analysis. If the spectrophotometer reads
7.1.8 Membrane particle filter: A membrane out in transmittance, convert to absorbance
filter of 0.8 to 2 μm porosity is used to pro- as follows:
tect the flow controller from particles dur-
ing long-term sampling. This item is op- A = log10 (1/T ) (1)
tional for short-term sampling. where:
7.1.9 Vacuum pump: A vacuum pump
equipped with a vacuum gauge and capable A = absorbance, and
of maintaining at least 70 kPa (0.7 atm) vac- T = transmittance (0<≥T<1).
uum differential across the flow control de- A standard wavelength filter traceable to
vice at the specified flow rate is required for the National Bureau of Standards is used to
sampling. verify the wavelength calibration according
7.1.10 Temperature control device: The tem- to the procedure enclosed with the filter.
perature of the absorbing solution during The wavelength calibration must be verified
sampling must be maintained at 15° ±10 °C. upon initial receipt of the instrument and
As soon as possible following sampling and after each 160 hours of normal use or every 6
until analysis, the temperature of the col- months, whichever occurs first.
lected sample must be maintained at 5° ±5 °C.
7.3.2 Spectrophotometer cells: A set of 1-cm
Where an extended period of time may elapse
path length cells suitable for use in the visi-
before the collected sample can be moved to
ble region is used during analysis. If the cells
the lower storage temperature, a collection
are unmatched, a matching correction factor
temperature near the lower limit of the 15
must be determined according to Section
±10 °C range should be used to minimize
10.1.
losses during this period. Thermoelectric
coolers specifically designed for this tem- 7.3.3 Temperature control device: The color
perature control are available commercially development step during analysis must be
and normally operate in the range of 5° to 15 conducted in an environment that is in the
°C. Small refrigerators can be modified to range of 20° to 30 °C and controlled to ±1 °C.
provide the required temperature control; Both calibration and sample analysis must
however, inlet lines must be insulated from be performed under identical conditions
the lower temperatures to prevent condensa- (within 1 °C). Adequate temperature control
tion when sampling under humid conditions. may be obtained by means of constant tem-
A small heating pad may be necessary when perature baths, water baths with manual
sampling at low temperatures (<7 °C) to pre- temperature control, or temperature con-
vent the absorbing solution from freez- trolled rooms.
ing.(17) 7.3.4 Glassware: Class A volumetric glass-
7.1.11 Sampling train container: The absorb- ware of various capacities is required for pre-
ing solution must be shielded from light dur- paring and standardizing reagents and stand-
ing and after sampling. Most commercially ards and for dispensing solutions during
available sampler trains are enclosed in a analysis. These included pipets, volumetric
light-proof box. flasks, and burets.
7.1.12 Timer: A timer is recommended to 7.3.5 TCM waste receptacle: A glass waste re-
ceptacle is required for the storage of spent
wreier-aviles on DSK5TPTVN1PROD with CFR

initiate and to stop sampling for the 24-hour

period. The timer is not a required piece of TCM solution. This vessel should be
equipment; however, without the timer a stoppered and stored in a hood at all times.
technician would be required to start and 8.0 Reagents.
stop the sampling manually. An elapsed time 8.1 Sampling.

22
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 Environmental Protection Agency Pt. 50, App. A–2
8.1.1 Distilled water: Purity of distilled 8.2.7 Potassium iodate solution: Accurately
water must be verified by the following pro- weigh to the nearest 0.1 mg, 1.5 g (record
cedure:(18) weight) of primary standard grade potassium
• Place 0.20 mL of potassium permanganate iodate that has been previously dried at 180
solution (0.316 g/L), 500 mL of distilled °C for at least 3 hours and cooled in a
water, and 1mL of concentrated sulfuric dessicator. Dissolve, then dilute to volume in
acid in a chemically resistant glass bottle, a 500-mL volumetric flask with distilled
stopper the bottle, and allow to stand. water.
• If the permanganate color (pink) does not 8.2.8 Stock sodium thiosulfate solution (0.1 N):
disappear completely after a period of 1 Prepare a stock solution by dissolving 25 g
hour at room temperature, the water is sodium thiosulfate (Na2 S2 O3÷5H2 O) in 1,000
suitable for use. mL freshly boiled, cooled, distilled water and
• If the permanganate color does disappear, adding 0.1 g sodium carbonate to the solu-
the water can be purified by redistilling tion. Allow the solution to stand at least 1
with one crystal each of barium hydroxide day before standardizing. To standardize, ac-
and potassium permanganate in an all curately pipet 50 mL of potassium iodate so-
glass still. lution (Section 8.2.7) into a 500-mL iodine
8.1.2 Absorbing reagent (0.04 M potassium flask and add 2.0 g of potassium iodide and 10
tetrachloromercurate [TCM]): Dissolve 10.86 mL of 1 N HCl. Stopper the flask and allow
g mercuric chloride, 0.066 g EDTA, and 6.0 g to stand for 5 minutes. Titrate the solution
potassium chloride in distilled water and di- with stock sodium thiosulfate solution (Sec-
lute to volume with distilled water in a 1,000- tion 8.2.8) to a pale yellow color. Add 5 mL of
mL volumetric flask. (Caution: Mercuric starch solution (Section 8.2.5) and titrate
chloride is highly poisonous. If spilled on until the blue color just disappears. Cal-
skin, flush with water immediately.) The pH culate the normality (Ns) of the stock so-
of this reagent should be between 3.0 and 5.0 dium thiosulfate solution as follows:
(10) Check the pH of the absorbing solution
W
by using pH indicating paper or a pH meter.
If the pH of the solution is not between 3.0
NS = × 2.80 (2)
and 5.0, dispose of the solution according to M
one of the disposal techniques described in where:
Section 13.0. The absorbing reagent is nor- M = volume of thiosulfate required in mL,
mally stable for 6 months. If a precipitate and
forms, dispose of the reagent according to W = weight of potassium iodate in g (re-
one of the procedures described in Section corded weight in Section 8.2.7).
13.0.
8.2 Analysis. 10 3 (conversion of g to mg) × 0.1(fraction iodate used )
2.80 =
8.2.1 Sulfamic acid (0.6%): Dissolve 0.6 g sul- 35.67 (equivalent weight of potassium iodate)
famic acid in 100 mL distilled water. Perpare 8.2.9 Working sodium thiosulfate titrant (0.01
fresh daily. N): Accurately pipet 100 mL of stock sodium
8.2.2 Formaldehyde (0.2%): Dilute 5 mL thiosulfate solution (Section 8.2.8) into a
formaldehyde solution (36 to 38 percent) to 1,000-mL volumetric flask and dilute to vol-
1,000 mL with distilled water. Prepare fresh ume with freshly boiled, cooled, distilled
daily. water. Calculate the normality of the work-
8.2.3 Stock iodine solution (0.1 N): Place 12.7 ing sodium thiosulfate titrant (NT) as fol-
g resublimed iodine in a 250-mL beaker and lows:
add 40 g potassium iodide and 25 mL water.
Stir until dissolved, transfer to a 1,000 mL
volumetric flask and dilute to volume with
N T = N S × 0.100 (3)
distilled water. 8.2.10 Standardized sulfite solution for the
8.2.4 Iodine solution (0.01 N): Prepare ap- preparation of working sulfite-TCM solution:
proximately 0.01 N iodine solution by dilut- Dissolve 0.30 g sodium metabisulfite (Na2 S2
ing 50 mL of stock iodine solution (Section O5) or 0.40 g sodium sulfite (Na2 SO3) in 500
8.2.3) to 500 mL with distilled water. mL of recently boiled, cooled, distilled
8.2.5 Starch indicator solution: Triturate 0.4 water. (Sulfite solution is unstable; it is
g soluble starch and 0.002 g mercuric iodide therefore important to use water of the high-
(preservative) with enough distilled water to est purity to minimize this instability.) This
EC08NO91.003</MATH>

form a paste. Add the paste slowly to 200 mL solution contains the equivalent of 320 to 400
of boiling distilled water and continue boil- μg SO2/mL. The actual concentration of the
ing until clear. Cool and transfer the solu- solution is determined by adding excess io-
tion to a glass stopperd bottle. dine and back-titrating with standard so-
wreier-aviles on DSK5TPTVN1PROD with CFR

8.2.6 1 N hydrochloric acid: Slowly and while dium thiosulfate solution. To back-titrate,
stirring, add 86 mL of concentrated hydro- pipet 50 mL of the 0.01 N iodine solution
EC08NO91.002</MATH>

chloric acid to 500 mL of distilled water. (Section 8.2.4) into each of two 500-mL iodine
Allow to cool and dilute to 1,000 mL with dis- flasks (A and B). To flask A (blank) add 25
tilled water. mL distilled water, and to flask B (sample)

23
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 Pt. 50, App. A–2 40 CFR Ch. I (7–1–14 Edition)
pipet 25 mL sulfite solution. Stopper the tinue the titration until the blue color just
flasks and allow to stand for 5 minutes. Pre- disappears.
pare the working sulfite-TCM solution (Sec- 8.2.11 Working sulfite-TCM solution: Accu-
tion 8.2.11) immediately prior to adding the rately pipet 5 mL of the standard sulfite so-
iodine solution to the flasks. Using a buret lution (Section 8.2.10) into a 250-mL volu-
containing standardized 0.01 N thiosulfate metric flask and dilute to volume with 0.04
titrant (Section 8.2.9), titrate the solution in M TCM. Calculate the concentration of sul-
each flask to a pale yellow color. Then add 5 fur dioxide in the working solution as fol-
mL starch solution (Section 8.2.5) and con- lows:

( A − B)( N T )(32,000)
C TCM / SO 2 (μg SO 2 /mL ) = × 0.02 ( 4)
25

where: percent potassium iodide (KI) solution in a

A = volume of thiosulfate titrant required 50-mL separatory funnel and shake thor-
for the blank, mL; oughly. If a yellow color appears in the alco-
B = volume of thiosulfate titrant required hol phase, redistill the 1-butanol from silver
for the sample, mL; oxide and collect the middle fraction or pur-
NT = normality of the thiosulfate titrant, chase a new supply of 1-butanol.
from equation (3); 2. Weigh 100 mg of pararosaniline hydro-
32,000 = milliequivalent weight of SO2, μg; chloride dye (PRA) in a small beaker. Add 50
25 = volume of standard sulfite solution, mL; mL of the equilibrated acid (drain in acid
and from the bottom of the separatory funnel in
0.02 = dilution factor. 1.) to the beaker and let stand for several
This solution is stable for 30 days if kept at minutes. Discard the remaining acid phase in
5 °C. (16) If not kept at 5 °C, prepare fresh the separatory funnel.
daily. 3. To a 125-mL separatory funnel, add 50
8.2.12 Purified pararosaniline (PRA) stock so- mL of the equilibrated 1-butanol (draw the 1-
lution (0.2% nominal): butanol from the top of the separatory fun-
8.2.12.1 Dye specifications— nel in 1.). Transfer the acid solution (from 2.)
• The dye must have a maximum absorbance containing the dye to the funnel and shake
at a wavelength of 540 nm when assayed in carefully to extract. The violet impurity will
a buffered solution of 0.1 M sodium ace- transfer to the organic phase.
tate-acetic acid; 4. Transfer the lower aqueous phase into
• The absorbance of the reagent blank, another separatory funnel, add 20 mL of
which is temperature sensitive (0.015 ab- equilibrated 1-butanol, and extract again.
sorbance unit/ °C), must not exceed 0.170 at 5. Repeat the extraction procedure with
22 °C with a 1-cm optical path length when three more 10-mL portions of equilibrated 1-
the blank is prepared according to the butanol.
specified procedure; 6. After the final extraction, filter the acid
• The calibration curve (Section 10.0) must phase through a cotton plug into a 50-mL
have a slope equal to 0.030 ±0.002 absorb- volumetric flask and bring to volume with 1
ance unit/μg SO2 with a 1-cm optical path N HCl. This stock reagent will be a yellowish
length when the dye is pure and the sulfite red.
solution is properly standardized. 7. To check the purity of the PRA, perform
8.2.12.2 Preparation of stock PRA solution—A the assay and adjustment of concentration
specially purified (99 to 100 percent pure) so- (Section 8.2.12.4) and prepare a reagent blank
lution of pararosaniline, which meets the (Section 11.2); the absorbance of this reagent
above specifications, is commercially avail- blank at 540 nm should be less than 0.170 at
able in the required 0.20 percent concentra- 22 °C. If the absorbance is greater than 0.170
tion (Harleco Co.). Alternatively, the dye under these conditions, further extractions
may be purified, a stock solution prepared, should be performed.
and then assayed according to the procedure 8.2.12.4 PRA assay procedure—The con-
as described below.(10) centration of pararosaniline hydrochloride
8.2.12.3 Purification procedure for PRA— (PRA) need be assayed only once after purifi-
1. Place 100 mL each of 1-butanol and 1 N cation. It is also recommended that commer-
cial solutions of pararosaniline be assayed
wreier-aviles on DSK5TPTVN1PROD with CFR

HCl in a large separatory funnel (250-mL)

and allow to equilibrate. Note: Certain when first purchased. The assay procedure is
batches of 1-butanol contain oxidants that as follows:(10)
create an SO2 demand. Before using, check 1. Prepare 1 M acetate-acetic acid buffer
by placing 20 mL of 1-butanol and 5 mL of 20 stock solution with a pH of 4.79 by dissolving

24
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 Environmental Protection Agency Pt. 50, App. A–2
13.61 g of sodium acetate trihydrate in dis- justed so that linearity is maintained be-
tilled water in a 100-mL volumetric flask. tween absorbance and concentration over the
Add 5.70 mL of glacial acetic acid and dilute dynamic range. Absorbing reagent volumes
to volume with distilled water. less than 10 mL are not recommended. The
2. Pipet 1 mL of the stock PRA solution ob- collection efficiency is above 98 percent for
tained from the purification process or from the conditions described; however, the effi-
a commercial source into a 100-mL volu- ciency may be substantially lower when
metric flask and dilute to volume with dis- sampling concentrations below 25 μgSO2/
tilled water. m3.(8,9)
3. Transfer a 5–mL aliquot of the diluted 9.2 30-Minute and 1-Hour Sampling. Place 10
PRA solution from 2. into a 50–mL volu-
mL of TCM absorbing reagent in a midget
metric flask. Add 5mL of 1 M acetate-acetic
impinger and seal the impinger with a thin
acid buffer solution from 1. and dilute the
film of silicon stopcock grease (around the
mixture to volume with distilled water. Let
the mixture stand for 1 hour. ground glass joint). Insert the sealed im-
4. Measure the absorbance of the above so- pinger into the sampling train as shown in
lution at 540 nm with a spectrophotometer Figure 1, making sure that all connections
against a distilled water reference. Compute between the various components are leak
the percentage of nominal concentration of tight. Greaseless ball joint fittings, heat
PRA by shrinkable Teflon ® tubing, or Teflon ® tube
fittings may be used to attain leakfree con-
A×K ditions for portions of the sampling train
%PRA = ( 5) that come into contact with air containing
W SO2. Shield the absorbing reagent from di-
where: rect sunlight by covering the impinger with
aluminum foil or by enclosing the sampling
A = measured absorbance of the final mix- train in a light-proof box. Determine the
ture (absorbance units); flow rate according to Section 9.4.2. Collect
W = weight in grams of the PRA dye used in the sample at 1 ±0.10 L/min for 30-minute
the assay to prepare 50 mL of stock solu-
sampling or 0.500 ±0.05 L/min for 1-hour sam-
tion (for example, 0.100 g of dye was used
pling. Record the exact sampling time in
to prepare 50 mL of solution in the puri-
minutes, as the sample volume will later be
fication procedure; when obtained from
determined using the sampling flow rate and
commercial sources, use the stated con-
centration to compute W; for 98% PRA, the sampling time. Record the atmospheric
W=.098 g.); and pressure and temperature.
K = 21.3 for spectrophotometers having a 9.3 24-Hour Sampling. Place 50 mL of TCM
spectral bandwidth of less than 15 nm absorbing solution in a large absorber, close
and a path length of 1 cm. the cap, and, if needed, apply the heat shrink
material as shown in Figure 3. Verify that
8.2.13 Pararosaniline reagent: To a 250–mL
volumetric flask, add 20 mL of stock PRA so- the reagent level is at the 50 mL mark on the
lution. Add an additional 0.2 mL of stock so- absorber. Insert the sealed absorber into the
lution for each percentage that the stock as- sampling train as shown in Figure 2. At this
says below 100 percent. Then add 25 mL of 3 time verify that the absorber temperature is
M phosphoric acid and dilute to volume with controlled to 15 ±10 °C. During sampling, the
distilled water. The reagent is stable for at absorber temperature must be controlled to
least 9 months. Store away from heat and prevent decomposition of the collected com-
light. plex. From the onset of sampling until anal-
9.0 Sampling Procedure. ysis, the absorbing solution must be pro-
9.1 General Considerations. Procedures are tected from direct sunlight. Determine the
described for short-term sampling (30-minute flow rate according to Section 9.4.2. Collect
and 1-hour) and for long-term sampling (24- the sample for 24 hours from midnight to
hour). Different combinations of absorbing midnight at a flow rate of 0.200 ±0.020 L/min.
reagent volume, sampling rate, and sampling A start/stop timer is helpful for initiating
time can be selected to meet special needs. and stopping sampling and an elapsed time
For combinations other than those specifi- meter will be useful for determining the
cally described, the conditions must be ad- sampling time.
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25
EC08NO91.005</MATH>

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 Pt. 50, App. A–2 40 CFR Ch. I (7–1–14 Edition)

9.4 Flow Measurement. For 24-hour samples, the standard flow rate
9.4.1 Calibration: Flow measuring devices is determined at the time the absorber is
used for the on-site flow measurements re- placed in the sampling train and again when
quired in 9.4.2 must be calibrated against a the absorber is removed from the train for
reliable flow or volume standard such as an shipment to the analytical laboratory with a
NBS traceable bubble flowmeter or cali- calibrated flow measuring device connected
brated wet test meter. Rotameters or crit- to the inlet of the sampling train. The flow
ical orifices used in the sampling train may rate determination must be made with all
be calibrated, if desired, as a quality control components of the sampling system in oper-
check, but such calibration shall not replace ation (e.g., the absorber temperature con-
the on-site flow measurements required by troller and any sample box heaters must also
9.4.2. In-line rotameters, if they are to be be operating). Equation 6 may be used to de-
calibrated, should be calibrated in situ, with termine the standard flow rate when a cali-
the appropriate volume of solution in the ab- brated positive displacement meter is used
sorber. as the flow measuring device. Other types of
9.4.2 Determination of flow rate at sampling calibrated flow measuring devices may also
wreier-aviles on DSK5TPTVN1PROD with CFR

site: For short-term samples, the standard be used to determine the flow rate at the
flow rate is determined at the sampling site sampling site provided that the user applies
at the initiation and completion of sample any appropriate corrections to devices for
collection with a calibrated flow measuring which output is dependent on temperature or
device connected to the inlet of the absorber. pressure.

26
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 Environmental Protection Agency Pt. 50, App. A–2

Pb − (1 − RH)PH 2 O 298.16.
Q std = Q act × × (6)
Pstd (Tmeter + 27316
. ).

where: wet volume standards only, i.e., bubble

Qstd = flow rate at standard conditions, std L/ flowmeter or wet test meter; for dry
min (25 °C and 760 mm Hg); standards, i.e., dry test meter, PH2O=0);
Qact = flow rate at monitoring site conditions, Pstd = standard barometric pressure, in the
L/min; same units as Pb (760 mm Hg or 101 kPa);
Pb = barometric pressure at monitoring site and
conditions, mm Hg or kPa; Tmeter = temperature of the air in the flow or
RH = fractional relative humidity of the air volume standard, °C (e.g., bubble flow-
being measured; meter).
PH2O = vapor pressure of water at the tem- If a barometer is not available, the fol-
perature of the air in the flow or volume lowing equation may be used to determine
standard, in the same units as Pb, (for the barometric pressure:

Pb = 760 −.076(H) mm Hg, or Pb = 101−.01(H)kPa (7)

where: ture is above 10 °C. Store the sample at 5° ±5

H = sampling site elevation above sea level °C until it is analyzed.
in meters. 10.0 Analytical Calibration.
10.1 Spectrophotometer Cell Matching. If un-
If the initial flow rate (Qi) differs from the matched spectrophotometer cells are used,
flow rate of the critical orifice or the flow an absorbance correction factor must be de-
rate indicated by the flowmeter in the sam- termined as follows:
pling train (Qc) by more than 5 percent as de- 1. Fill all cells with distilled water and des-
termined by equation (8), check for leaks and ignate the one that has the lowest absorb-
redetermine Qi. ance at 548 nm as the reference. (This ref-
erence cell should be marked as such and
Qi − Qc continually used for this purpose throughout
% Diff = ×100 ( 8) all future analyses.)
Qc 2. Zero the spectrophotometer with the ref-
Invalidate the sample if the difference be- erence cell.
tween the initial (Qi) and final (Qf) flow rates 3. Determine the absorbance of the remain-
is more than 5 percent as determined by ing cells (Ac) in relation to the reference cell
equation (9): and record these values for future use. Mark
all cells in a manner that adequately identi-

EC08NO91.010</MATH>
Qi − Qf fies the correction.
% Diff = ×100 ( 9) The corrected absorbance during future
analyses using each cell is determining as
Qf follows:
9.5 Sample Storage and Shipment. Remove
the impinger or absorber from the sampling A = A obs − A c (10 )
train and stopper immediately. Verify that EC08NO91.009</MATH>
where:
the temperature of the absorber is not above
25 °C. Mark the level of the solution with a A = corrected absorbance,
temporary (e.g., grease pencil) mark. If the Aobs = uncorrected absorbance, and
sample will not be analyzed within 12 hours Ac = cell correction.
of sampling, it must be stored at 5° ±5 °C 10.2 Static Calibration Procedure (Option 1).
EC08NO91.008</MATH>

until analysis. Analysis must occur within 30 Prepare a dilute working sulfite-TCM solu-
days. If the sample is transported or shipped tion by diluting 10 mL of the working sul-
for a period exceeding 12 hours, it is rec- fite-TCM solution (Section 8.2.11) to 100 mL
ommended that thermal coolers using with TCM absorbing reagent. Following the
wreier-aviles on DSK5TPTVN1PROD with CFR

eutectic ice packs, refrigerated shipping con- table below, accurately pipet the indicated
tainers, etc., be used for periods up to 48 volumes of the sulfite-TCM solutions into a
EC08NO91.007</MATH>

hours. (17) Measure the temperature of the series of 25-mL volumetric flasks. Add TCM
absorber solution when the shipment is re- absorbing reagent as indicated to bring the
ceived. Invalidate the sample if the tempera- volume in each flask to 10 mL.

27
EC08NO91.006</MATH>

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 Pt. 50, App. A–2 40 CFR Ch. I (7–1–14 Edition)

Volume timer that has been set for 30 minutes. Bring

Volume Total μg
of sulfite- all flasks to volume with recently boiled and
Sulfite-TCM solution of TCM, SO2
TCM so- cooled distilled water and mix thoroughly.
mL (approx.*
lution
The color must be developed (during the 30-
Working ......................... 4.0 6.0 28.8 minute period) in a temperature environ-
Working ......................... 3.0 7.0 21.6 ment in the range of 20° to 30 °C, which is
Working ......................... 2.0 8.0 14.4 controlled to ±1 °C. For increased precision,
Dilute working ................ 10.0 0.0 7.2 a constant temperature bath is rec-
Dilute working ................ 5.0 5.0 3.6 ommended during the color development
0.0 10.0 0.0
step. After 30 minutes, determine the cor-
*Based on working sulfite-TCM solution concentration of 7.2 rected absorbance of each standard at 548 nm
μg SO2/mL; the actual total μg SO2 must be calculated using against a distilled water reference (Section
equation 11 below.
10.1). Denote this absorbance as (A). Distilled
To each volumetric flask, add 1 mL 0.6% water is used in the reference cell rather
sulfamic acid (Section 8.2.1), accurately than the reagant blank because of the tem-
pipet 2 mL 0.2% formaldehyde solution (Sec- perature sensitivity of the reagent blank.
tion 8.2.2), then add 5 mL pararosaniline so- Calculate the total micrograms SO2 in each
lution (Section 8.2.13). Start a laboratory solution:

μg SO 2 = VTCM / SO 2 × C TCM / SO 2 × D (11)

where: a low flow of dry carrier gas to a mixing

VTCM/SO2 = volume of sulfite-TCM solution chamber where it is diluted with SO2-free air
used, mL; to the desired concentration and supplied to
CTCM/SO2 = concentration of sulfur dioxide in a vented manifold. A typical system is shown
the working sulfite-TCM, μg SO2/mL schematically in Figure 4 and this system
(from equation 4); and and other similar systems have been de-
D = dilution factor (D = 1 for the working scribed in detail by O’Keeffe and Ortman; (19)
sulfite-TCM solution; D = 0.1 for the di- Scaringelli, Frey, and Saltzman, (20) and
luted working sulfite-TCM solution). Scaringelli, O’Keeffe, Rosenberg, and Bell.
A calibration equation is determined using (21) Permeation devices may be prepared or
the method of linear least squares (Section purchased and in both cases must be trace-
12.1). The total micrograms SO2 contained in able either to a National Bureau of Stand-
each solution is the x variable, and the cor- ards (NBS) Standard Reference Material
rected absorbance (eq. 10) associated with (SRM 1625, SRM 1626, SRM 1627) or to an
each solution is the y variable. For the cali- NBS/EPA-approved commercially available
bration to be valid, the slope must be in the Certified Reference Material (CRM). CRM’s
range of 0.030 ±0.002 absorbance unit/μg SO2, are described in Reference 22, and a list of
the intercept as determined by the least CRM sources is available from the address
squares method must be equal to or less than shown for Reference 22. A recommended pro-
0.170 absorbance unit when the color is devel- tocol for certifying a permeation device to
oped at 22 °C (add 0.015 to this 0.170 specifica- an NBS SRM or CRM is given in Section 2.0.7
tion for each °C above 22 °C) and the correla- of Reference 2. Device permeation rates of 0.2
tion coefficient must be greater than 0.998. If
to 0.4 μg/min, inert gas flows of about 50 mL/
these criteria are not met, it may be the re-
min, and dilution air flow rates from 1.1 to 15
sult of an impure dye and/or an improperly
L/min conveniently yield standard
standardized sulfite-TCM solution. A calibra-
atmospheres in the range of 25 to 600 μg SO2/
tion factor (Bs) is determined by calculating
the reciprocal of the slope and is subse- m3 (0.010 to 0.230 ppm).
quently used for calculating the sample con- 10.3.1 Calibration Option 2A (30-minute and
centration (Section 12.3). 1-hour samples): Generate a series of six
10.3 Dynamic Calibration Procedures (Option standard atmospheres of SO2 (e.g., 0, 50, 100,
2). Atmospheres containing accurately 200, 350, 500, 750 μg/m3) by adjusting the dilu-
known concentrations of sulfur dioxide are tion flow rates appropriately. The concentra-
prepared using permeation devices. In the tion of SO2 in each atmosphere is calculated
systems for generating these atmospheres, as follows:
the permeation device emits gaseous SO2 at
3
Pr × 10
wreier-aviles on DSK5TPTVN1PROD with CFR

a known, low, constant rate, provided the

temperature of the device is held constant Ca = (12 )
ER31AU93.014</MATH>

(±0.1 °C) and the device has been accurately Qd + Qp

calibrated at the temperature of use. The
SO2 permeating from the device is carried by where:

28
EC08NO91.011</MATH>

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 Environmental Protection Agency Pt. 50, App. A–2
Ca = concentration of SO2 at standard condi- Qd = flow rate of dilution air, std L/min; and
tions, μg/m3; Qp = flow rate of carrier gas across perme-
Pr = permeation rate, μg/min; ation device, std L/min.
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29
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 Pt. 50, App. A–2 40 CFR Ch. I (7–1–14 Edition)
Be sure that the total flow rate of the
standard exceeds the flow demand of the Vb × C s
t= (14 )
sample train, with the excess flow vented at −3
atmospheric pressure. Sample each atmos- C a × Q s × 10
phere using similar apparatus as shown in where:
Figure 1 and under the same conditions as t = sampling time, min;
field sampling (i.e., use same absorbing rea- Vb = volume of absorbing solution used for
gent volume and sample same volume of air sampling (50 mL);
at an equivalent flow rate). Due to the Cs = desired concentration of SO2 in the ab-
length of the sampling periods required, this sorbing solution, μg/mL;
method is not recommended for 24-hour sam- Ca = concentration of the standard atmos-
pling. At the completion of sampling, quan- phere calculated according to equation
titatively transfer the contents of each im- 12, μg/m3; and
pinger to one of a series of 25-mL volumetric Qs = sampling flow rate, std L/min.
flasks (if 10 mL of absorbing solution was At the completion of sampling, bring the
used) using small amounts of distilled water absorber solutions to original volume with
for rinse (<5mL). If >10 mL of absorbing solu- distilled water. Pipet a 10-mL portion from
tion was used, bring the absorber solution in each absorber into one of a series of 25-mL
each impinger to orginal volume with dis- volumetric flasks. If the color development
tilled H2 O and pipet 10-mL portions from steps are not to be started within 12 hours of
each impinger into a series of 25-mL volu- sampling, store the solutions at 5° ±5 °C. Add
metric flasks. If the color development steps the remaining reagents for color develop-
are not to be started within 12 hours of sam- ment in the same manner as in Section 10.2
pling, store the solutions at 5° ±5 °C. Cal- for static solutions. Calculate the total μg
culate the total micrograms SO2 in each so- SO2 in each standard as follows:
lution as follows: −3
C a × Q s × t × Va × 10
C a × Q s × t × Va × 10
−3 μgSO 2 = (15)
μgSO 2 = (13) Vb
Vb
where:
where: Va = volume of absorbing solution used for
Ca = concentration of SO2 in the standard at- color development (10 mL).
mosphere, μg/m3; All other parameters are defined in equation
Os = sampling flow rate, std L/min; 14.
t=sampling time, min; Calculate a calibration equation and a
Va = volume of absorbing solution used for calibration factor (Bt) according to Section
color development (10 mL); and 10.2 adhering to all the specified criteria.
Vb = volume of absorbing solution used for 11.0 Sample Preparation and Analysis.
sampling, mL. 11.1 Sample Preparation. Remove the sam-
ples from the shipping container. If the ship-
Add the remaining reagents for color de- ment period exceeded 12 hours from the com-
velopment in the same manner as in Section pletion of sampling, verify that the tempera-
10.2 for static solutions. Calculate a calibra- ture is below 10 °C. Also, compare the solu-
tion equation and a calibration factor (Bg) tion level to the temporary level mark on
according to Section 10.2, adhering to all the the absorber. If either the temperature is
specified criteria. above 10 °C or there was significant loss
10.3.2 Calibration Option 2B (24-hour sam- (more than 10 mL) of the sample during ship-
ples): Generate a standard atmosphere con- ping, make an appropriate notation in the
taining approximately 1,050 μg SO2/m3 and record and invalidate the sample. Prepare
calculate the exact concentration according the samples for analysis as follows:
to equation 12. Set up a series of six absorb- 1. For 30-minute or 1-hour samples: Quan-
ers according to Figure 2 and connect to a titatively transfer the entire 10 mL amount
common manifold for sampling the standard of absorbing solution to a 25-mL volumetric
atmosphere. Be sure that the total flow rate flask and rinse with a small amount (<5 mL)
of distilled water.
ER31AU93.017</MATH>

of the standard exceeds the flow demand at

the sample manifold, with the excess flow 2. For 24-hour samples: If the volume of the
sample is less than the original 50-mL vol-
vented at atmospheric pressure. The absorb-
ume (permanent mark on the absorber), ad-
ers are then allowed to sample the atmos-
just the volume back to the original volume
phere for varying time periods to yield solu-
wreier-aviles on DSK5TPTVN1PROD with CFR

with distilled water to compensate for water

tions containing 0, 0.2, 0.6, 1.0, 1.4, 1.8, and 2.2 lost to evaporation during sampling. If the
ER31AU93.016</MATH>

μg SO2/mL solution. The sampling times re- final volume is greater than the original vol-
quired to attain these solution concentra- ume, the volume must be measured using a
tions are calculated as follows: graduated cylinder. To analyze, pipet 10 mL

30
ER31AU93.015</MATH>

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 Environmental Protection Agency Pt. 50, App. A–2
of the solution into a 25-mL volumetric is used to calculate a calibration equation in
flask. the form of:
11.2 Sample Analysis. For each set of deter-
minations, prepare a reagent blank by add- y = mx + b (16 )
ing 10 mL TCM absorbing solution to a 25-
mL volumetric flask, and two control stand- where:
ards containing approximately 5 and 15 μg y = corrected absorbance,
SO2, respectively. The control standards are m = slope, absorbance unit/μg SO2,
prepared according to Section 10.2 or 10.3. x = micrograms of SO2,
The analysis is carried out as follows: b = y intercept (absorbance units).
1. Allow the sample to stand 20 minutes The slope (m), intercept (b), and correla-
after the completion of sampling to allow tion coefficient (r) are calculated as follows:
any ozone to decompose (if applicable).
2. To each 25-mL volumetric flask con- n ∑ xy − ( ∑ x)( ∑ y)
taining reagent blank, sample, or control m= (17)
standard, add 1 mL of 0.6% sulfamic acid n ∑ x 2 − ( ∑ x )2
(Section 8.2.1) and allow to react for 10 min.
3. Accurately pipet 2 mL of 0.2% formalde- ∑y − m∑x
b= (18 )
hyde solution (Section 8.2.2) and then 5 mL n
of pararosaniline solution (Section 8.2.13)
into each flask. Start a laboratory timer set
m ( ∑ xy − ∑ x ∑ y / n )
at 30 minutes. r= (19 )
4. Bring each flask to volume with recently 2 2
∑ y − (∑ y) / n
boiled and cooled distilled water and mix
thoroughly. where n is the number of calibration points.
5. During the 30 minutes, the solutions A data form (Figure 5) is supplied for eas-
must be in a temperature controlled environ- ily organizing calibration data when the
ment in the range of 20° to 30 °C maintained slope, intercept, and correlation coefficient
to ±1 °C. This temperature must also be with- are calculated by hand.
in 1 °C of that used during calibration. 12.2 Total Sample Volume. Determine the
6. After 30 minutes and before 60 minutes, sampling volume at standard conditions as
determine the corrected absorbances (equa- follows:
tion 10) of each solution at 548 nm using 1-cm
optical path length cells against a distilled Qi + Qf
Vstd = ×t ( 20 )
water reference (Section 10.1). (Distilled water
is used as a reference instead of the reagent 2
blank because of the sensitivity of the reagent where:
blank to temperature.) Vstd = sampling volume in std L,
7. Do not allow the colored solution to Qi = standard flow rate determined at the

ER31AU93.022</MATH>
stand in the cells because a film may be de- initiation of sampling in std L/min,
posited. Clean the cells with isopropyl alco- Qf = standard flow rate determined at the
hol after use. completion of sampling is std L/min, and
8. The reagent blank must be within 0.03 t = total sampling time, min.
absorbance units of the intercept of the cali-
bration equation determined in Section 10. 12.3 Sulfur Dioxide Concentration. Calculate
and report the concentration of each sample

ER31AU93.021</MATH>
11.3 Absorbance range. If the absorbance of
the sample solution ranges between 1.0 and as follows:
2.0, the sample can be diluted 1:1 with a por- 3
tion of the reagent blank and the absorbance 3 ( A − A o )( B x )(10 ) Vb
redetermined within 5 minutes. Solutions μg SO 2 /m = × ( 21)
with higher absorbances can be diluted up to Vstd Va
sixfold with the reagent blank in order to ob-
ER31AU93.020</MATH>
tain scale readings of less than 1.0 absorb- where:
ance unit. However, it is recommended that A = corrected absorbance of the sample solu-
a smaller portion (<10 mL) of the original tion, from equation (10);
sample be reanalyzed (if possible) if the sam- Ao = corrected absorbance of the reagent
ple requires a dilution greater than 1:1. blank, using equation (10);
11.4 Reagent disposal. All reagents con- BX = calibration factor equal to Bs, Bg, or Bt
ER31AU93.018</MATH> ER31AU93.019</MATH>

taining mercury compounds must be stored depending on the calibration procedure

and disposed of using one of the procedures used, the reciprocal of the slope of the
contained in Section 13. Until disposal, the calibration equation;
discarded solutions can be stored in closed Va = volume of absorber solution analyzed,
wreier-aviles on DSK5TPTVN1PROD with CFR

glass containers and should be left in a fume mL;

hood. Vb = total volume of solution in absorber (see
12.0 Calculations. 11.1–2), mL; and
12.1 Calibration Slope, Intercept, and Correla- Vstd = standard air volume sampled, std L
tion Coefficient. The method of least squares (from Section 12.2).

31
EC08NO91.012</MATH>

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 Pt. 50, App. A–2 40 CFR Ch. I (7–1–14 Edition)

DATA FORM 5. After 24 hours, allow the solution to

[For hand calculations] stand without stirring to allow the mercury
amalgam (solid black material) to settle to
Calibra- the bottom of the waste receptacle.
Micro- Absor-
tion point grams So 6. Upon settling, decant and discard the su-
2 bance units
no.
pernatant liquid.
(x) (y) x2 xy y2 7. Quantitatively transfer the solid mate-
1 ........... .................. ................... .......... .......... ........ rial to a container and allow to dry.
2 ........... .................. ................... .......... .......... ........ 8. The solid material can be sent to a mer-
3 ........... .................. ................... .......... .......... ........ cury reclaiming plant. It must not be dis-
4 ........... .................. ................... .......... .......... ........ carded.
5 ........... .................. ................... .......... .......... ........ 13.3 Method Using Aluminum Foil Strips.
6 ........... .................. ................... .......... .......... ........ 1. Place the waste solution in an uncapped
vessel in a hood.
S x=lll S y=lll S x =lll Sxylll 2 2. For each liter of waste solution, add ap-
Sy2lll proximately 10 g of aluminum foil strips. If
n=lll (number of pairs of coordinates.) all the aluminum is consumed and no gas is
llllllllllllllllllllllll evolved, add an additional 10 g of foil. Repeat
until the foil is no longer consumed and
FIGURE 5. Data form for hand calculations.
allow the gas to evolve for 24 hours.
12.4 Control Standards. Calculate the ana- 3. Decant the supernatant liquid and dis-
lyzed micrograms of SO2 in each control card.
standard as follows: 4. Transfer the elemental mercury that has
settled to the bottom of the vessel to a stor-
(
C q = A − A o × Bx ) (22) age container.
5. The mercury can be sent to a mercury
where: reclaiming plant. It must not be discarded.
Cq = analyzed μg SO2 in each control stand- 14.0 References for SO2 Method.
ard, 1. Quality Assurance Handbook for Air Pol-
A = corrected absorbance of the control lution Measurement Systems, Volume I,
standard, and Principles. EPA–600/9–76–005, U.S. Environ-
Ao = corrected absorbance of the reagent mental Protection Agency, Research Tri-
blank. angle Park, NC 27711, 1976.
2. Quality Assurance Handbook for Air Pol-
The difference between the true and ana-
lution Measurement Systems, Volume II,
lyzed values of the control standards must
Ambient Air Specific Methods. EPA–600/4–77–
not be greater than 1 μg. If the difference is
027a, U.S. Environmental Protection Agency,
greater than 1 μg, the source of the discrep-
Research Triangle Park, NC 27711, 1977.
ancy must be identified and corrected.
3. Dasqupta, P. K., and K. B. DeCesare. Sta-
12.5 Conversion of μg/m3 to ppm (v/v). If de-
bility of Sulfur Dioxide in Formaldehyde and
sired, the concentration of sulfur dioxide at
Its Anomalous Behavior in
reference conditions can be converted to ppm
Tetrachloromercurate (II). Submitted for
SO2 (v/v) as follows:
publication in Atmospheric Environment, 1982.
μg SO 2 4. West, P. W., and G. C. Gaeke. Fixation of
−4
ppm SO 2 = × 3.82 × 10 ( 23) Sulfur Dioxide as Disulfitomercurate (II) and
3 Subsequent Colorimetric Estimation. Anal.
m
Chem., 28:1816, 1956.
13.0 The TCM absorbing solution and any 5. Ephraim, F. Inorganic Chemistry. P. C.
reagents containing mercury compounds L. Thorne and E. R. Roberts, Eds., 5th Edi-
must be treated and disposed of by one of the tion, Interscience, 1948, p. 562.
methods discussed below. Both methods re- 6. Lyles, G. R., F. B. Dowling, and V. J.
move greater than 99.99 percent of the mer- Blanchard. Quantitative Determination of
cury. Formaldehyde in the Parts Per Hundred Mil-
13.1 Disposal of Mercury-Containing Solu- lion Concentration Level. J. Air. Poll. Cont.
tions. Assoc., Vol. 15(106), 1965.
13.2 Method for Forming an Amalgam. 7. McKee, H. C., R. E. Childers, and O.
1. Place the waste solution in an uncapped Saenz, Jr. Collaborative Study of Reference
vessel in a hood. Method for Determination of Sulfur Dioxide
2. For each liter of waste solution, add ap- in the Atmosphere (Pararosaniline Method).
proximately 10 g of sodium carbonate until EPA-APTD-0903, U.S. Environmental Protec-
neutralization has occurred (NaOH may have tion Agency, Research Triangle Park, NC
to be used). 27711, September 1971.
3. Following neutralization, add 10 g of
wreier-aviles on DSK5TPTVN1PROD with CFR

8. Urone, P., J. B. Evans, and C. M. Noyes.

granular zinc or magnesium. Tracer Techniques in Sulfur—Air Pollution
ER31AU93.023</MATH>

4. Stir the solution in a hood for 24 hours. Studies Apparatus and Studies of Sulfur Di-
Caution must be exercised as hydrogen gas is oxide Colorimetric and Conductometric
evolved by this treatment process. Methods. Anal. Chem., 37: 1104, 1965.

32
EC08NO91.070</MATH>

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 Environmental Protection Agency Pt. 50, App. B
9. Bostrom, C. E. The Absorption of Sulfur (MD–77), Research Triangle Park, NC 27711,
Dioxide at Low Concentrations (pphm) Stud- January 1981.
ied by an Isotopic Tracer Method. Intern. J.
[47 FR 54899, Dec. 6, 1982; 48 FR 17355, Apr. 22,
Air Water Poll., 9:333, 1965. 1983. Redesignated at 75 FR 35595, June 22,
10. Scaringelli, F. P., B. E. Saltzman, and 2010]
S. A. Frey. Spectrophotometric Determina-
tion of Atmospheric Sulfur Dioxide. Anal. APPENDIX B TO PART 50—REFERENCE
Chem., 39: 1709, 1967. METHOD FOR THE DETERMINATION OF
11. Pate, J. B., B. E. Ammons, G. A. Swan- SUSPENDED PARTICULATE MATTER IN
son, and J. P. Lodge, Jr. Nitrite Interference
THE ATMOSPHERE (HIGH-VOLUME
in Spectrophotometric Determination of At-
mospheric Sulfur Dioxide. Anal. Chem., METHOD)
37:942, 1965. 1.0 Applicability.
12. Zurlo, N., and A. M. Griffini. Measure- 1.1 This method provides a measurement of
ment of the Sulfur Dioxide Content of the the mass concentration of total suspended
Air in the Presence of Oxides of Nitrogen and particulate matter (TSP) in ambient air for
Heavy Metals. Medicina Lavoro, 53:330, 1962. determining compliance with the primary
13. Rehme, K. A., and F. P. Scaringelli. Ef- and secondary national ambient air quality
fect of Ammonia on the Spectrophotometric standards for particulate matter as specified
Determination of Atmospheric Concentra- in § 50.6 and § 50.7 of this chapter. The meas-
tions of Sulfur Dioxide. Anal. Chem., 47:2474, urement process is nondestructive, and the
1975. size of the sample collected is usually ade-
14. McCoy, R. A., D. E. Camann, and H. C. quate for subsequent chemical analysis.
McKee. Collaborative Study of Reference Quality assurance procedures and guidance
Method for Determination of Sulfur Dioxide are provided in part 58, appendixes A and B,
in the Atmosphere (Pararosaniline Method) of this chapter and in References 1 and 2.
(24-Hour Sampling). EPA–650/4–74–027, U.S. 2.0 Principle.
Environmental Protection Agency, Research 2.1 An air sampler, properly located at the
Triangle Park, NC 27711, December 1973. measurement site, draws a measured quan-
15. Fuerst, R. G. Improved Temperature tity of ambient air into a covered housing
Stability of Sulfur Dioxide Samples Col- and through a filter during a 24-hr (nominal)
lected by the Federal Reference Method. sampling period. The sampler flow rate and
EPA–600/4–78–018, U.S. Environmental Pro- the geometry of the shelter favor the collec-
tection Agency, Research Triangle Park, NC tion of particles up to 25–50 μm (aerodynamic
27711, April 1978. diameter), depending on wind speed and di-
16. Scaringelli, F. P., L. Elfers, D. Norris, rection.(3) The filters used are specified to
and S. Hochheiser. Enhanced Stability of have a minimum collection efficiency of 99
Sulfur Dioxide in Solution. Anal. Chem., percent for 0.3 μm (DOP) particles (see Sec-
42:1818, 1970. tion 7.1.4).
2.2 The filter is weighed (after moisture
17. Martin, B. E. Sulfur Dioxide Bubbler
equilibration) before and after use to deter-
Temperature Study. EPA–600/4–77–040, U.S.
mine the net weight (mass) gain. The total
Environmental Protection Agency, Research
volume of air sampled, corrected to EPA
Triangle Park, NC 27711, August 1977.
standard conditions (25 °C, 760 mm Hg [101
18. American Society for Testing and Mate-
kPa]), is determined from the measured flow
rials. ASTM Standards, Water; Atmospheric
rate and the sampling time. The concentra-
Analysis. Part 23. Philadelphia, PA, October
tion of total suspended particulate matter in
1968, p. 226.
the ambient air is computed as the mass of
19. O’Keeffe, A. E., and G. C. Ortman. Pri- collected particles divided by the volume of
mary Standards for Trace Gas Analysis. air sampled, corrected to standard condi-
Anal. Chem., 38:760, 1966. tions, and is expressed in micrograms per
20. Scaringelli, F. P., S. A. Frey, and B. E. standard cubic meter (μg/std m3). For sam-
Saltzman. Evaluation of Teflon Permeation ples collected at temperatures and pressures
Tubes for Use with Sulfur Dioxide. Amer. significantly different than standard condi-
Ind. Hygiene Assoc. J., 28:260, 1967. tions, these corrected concentrations may
21. Scaringelli, F. P., A. E. O’Keeffe, E. differ substantially from actual concentra-
Rosenberg, and J. P. Bell, Preparation of tions (micrograms per actual cubic meter),
Known Concentrations of Gases and Vapors particularly at high elevations. The actual
With Permeation Devices Calibrated Gravi- particulate matter concentration can be cal-
metrically. Anal. Chem., 42:871, 1970. culated from the corrected concentration
22. A Procedure for Establishing using the actual temperature and pressure
wreier-aviles on DSK5TPTVN1PROD with CFR

Traceability of Gas Mixtures to Certain Na- during the sampling period.

tional Bureau of Standards Standard Ref- 3.0 Range.
erence Materials. EPA–600/7–81–010, U.S. En- 3.1 The approximate concentration range
vironmental Protection Agency, Environ- of the method is 2 to 750 μg/std m3. The upper
mental Monitoring Systems Laboratory limit is determined by the point at which the

33

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