ASTM D2914-95
(Test Method)Standard Test Methods for Sulfur Dioxide Content of the Atmosphere (West-Gaeke Method)
Standard Test Methods for Sulfur Dioxide Content of the Atmosphere (West-Gaeke Method)
SCOPE
1.1 These test methods cover the bubbler collection and colorimetric determination of sulfur dioxide (SO2) in the ambient or workplace atmosphere.
1.2 These test methods are applicable for determining SO2 over the range from approximately 25 µg/m3 (0.01 ppm(v)) to 1000 µg/m3 (0.4 ppm(v)), corresponding to a solution concentration of 0.03 µg SO2/mL to 1.3 µg SO2/mL. Beer's law is followed through the working analytical range from 0.02 µg SO2/mL to 1.4 µg SO2/mL.
1.3 The lower limit of detection is 0.075 µg SO2/mL(1), representing an air concentration of 25 µg SO2/m3 (0.01 ppm(v)) in a 30-min sample, or 13 µg SO2/m3 (0.005 ppm(v)) in a 24-h sample.
1.4 These test methods incorporate sampling for periods between 30 min and 24 h.
1.5 These test methods describe the determination of the collected (impinged) samples. A Method A and a Method B are described.
1.6 Method A is preferred over Method B, as it gives the higher sensitivity, but it has a higher blank. Manual Method B is pH-dependent, but is more suitable with spectrometers having a spectral band width greater than 20 nm.
Note 1--These test methods are applicable at concentrations below 25 µg/m 3 by sampling larger volumes of air if the absorption efficiency of the particular system is first determined, as described in Annex A4.
Note 2--Concentrations higher than 1000 µg/m 3 can be determined by using smaller gas volumes, larger collection volumes, or by suitable dilution of the collected sample with absorbing solution prior to analysis.
1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For specific precautionary statements, see 8.3.1, Section 9 , and A3.1.1
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Designation: D 2914 – 95 An American National Standard
Standard Test Methods for
Sulfur Dioxide Content of the Atmosphere (West-Gaeke
Method)
This standard is issued under the fixed designation D 2914; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
1.1 These test methods cover the bubbler collection and
priate safety and health practices and determine the applica-
colorimetric determination of sulfur dioxide (SO)inthe
bility of regulatory limitations prior to use. For specific
ambient or workplace atmosphere.
precautionary statements, see 8.3.7, Section 9, and A3.1.1.
1.2 These test methods are applicable for determining SO
over the range from approximately 25 μg/m (0.01 ppm) to
2. Referenced Documents
1000 μg/m (0.4 ppm), corresponding to a solution concentra-
2.1 ASTM Standards:
tion of 0.03 μg SO /mL to 1.3 μg SO /mL. Beer’s law is
2 2
D 1071 Test Methods for Volumetric Measurement of Gas-
followed through the working analytical range from 0.02 μg
eous Fuel Samples
SO /mL to 1.4 μg SO /mL.
2 2
D 1193 Specification for Reagent Water
1.3 The limit of detection, corresponding to twice the
D 1356 Terminology Relating to Sampling and Analysis of
standard deviation, is 0.02 μg SO /mL, representing an air
3 Atmospheres
concentration of 4 μg SO /m (0.0015 ppm) in a 24-h sample,
D 1357 Practice for Planning the Sampling of the Ambient
or7μgSO /m (0.003 ppm) in a 1-h sample.
Atmosphere
1.4 These test methods incorporate sampling for 1 h and for
D 1605 Practices for Sampling Atmospheres for Analysis of
24 h.
Gases and Vapors
1.5 These test methods describe manual and automated
D 1914 Practice for Conversion Units and Factors Relating
determinations of the collected (impinged) samples. Each
to Sampling and Analysis of Atmospheres
method of determination has two submethods designated as
D 3195 Practice for Rotameter Calibration
Manual Methods A and B and Automated Methods I and II.
D 3609 Practice for Calibration Techniques Using Perme-
The automated methods can determine 30 impinged samples
ation Tubes
per hour or 40 impinged samples per hour, depending upon the
D 3631 Test Methods for Measuring Surface Atmospheric
choice of instruments.
Pressure
1.6 Manual Method A is preferred over Manual Method B,
E 1 Specification for ASTM Thermometers
as it gives the higher sensitivity, but it has a higher blank.
E 275 Practice for Describing and Measuring Performance
Method B is pH-dependent, but is more suitable with spec-
of Ultraviolet, Visible, and Near-Infrared Spectrophotom-
trometers having a spectral band width greater than 20 nm.
eters
1.7 Automated Method II is preferred over Automated
Method I, as it gives the better precision. However, choice of
3. Terminology
method will be dictated by availability of equipment.
3.1 For definitions of terms used in this method, refer to
NOTE 1—These test methods are applicable at concentrations below 25
Terminology D 1356.
μg/m by sampling larger volumes of air if the absorption efficiency of the
particular system is first determined, as described in Annex A4.
4. Summary of Test Methods
NOTE 2—Concentrations higher than 1000 μg/m can be determined by
4.1 Sulfur dioxide (SO ) is absorbed by aspirating a mea-
using smaller gas volumes, larger collection volumes, or by suitable
sured air sample through a tetrachloromercurate (TCM) solu-
dilution of the collected sample.
tion, resulting in the formation of a dichlorosulfonatomercurate
1.8 This standard does not purport to address all of the
Annual Book of ASTM Standards, Vol 05.05.
1 3
These test methods are under the jurisdiction of ASTM Committee D-22 on Annual Book of ASTM Standards, Vol 11.01.
Sampling and Analysis of Atmospheresand are the direct responsibility of Subcom- Annual Book of ASTM Standards, Vol 11.03.
mittee D22.03 on Ambient Atmospheres and Source Emissions. Discontinued—See 1991 Annual Book of ASTM Standards, Vol 11.03.
Current edition approved Jan. 15, 1995. Published March 1995. Originally Annual Book of ASTM Standards, Vol 14.03.
published as D2914 – 70 T. Last previous edition D2914 – 91. Annual Book of ASTM Standards, Vol 03.06.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
D 2914
complex (1, 2). Ethylenediaminetetraacetic acid disodium salt long, with a polypropylene two-port closure (rubber stoppers
(EDTA) is added to this solution to complex heavy metals that are unacceptable because they cause high and variable blank
interfere with this method (3). Dichlorosulfonatomercurate, values). The closure shall be fitted with a 8-mm outside
once formed, is stable to strong oxidants (for example, ozone diameter, 6-mm inside diameter glass orifice tube approxi-
and oxides of nitrogen) (1). After the absorption is completed, mately 150 mm long, having the end drawn out to form an
any ozone in the solution is allowed to decay (4). The liquid is orifice of 0.4 6 0.1 mm and positioned to allow a clearance of
treated first with a solution of sulfamic acid to destroy the 6 mm from the orifice to the bottom of the tube.
nitrite anion formed from the absorption of oxides of nitrogen 7.1.3 Air Sample Probe—TFE-fluorocarbon, polypropy-
present in the atmosphere (5). It is treated next with solutions lene, or glass tube with a polypropylene or glass funnel at the
of formaldehyde and specially purified acid-bleached pararo- end.
saniline containing phosphoric acid (H PO ) to control pH. 7.1.4 Moisture Trap—Glass or polypropylene tube
3 4
Pararosaniline, formaldehyde, and the bisulfite anion react to equipped with a two-port closure. The entrance port of the
form the intensely colored pararosaniline methyl sulfonic acid closure is fitted with tubing that extends to the bottom of the
which behaves as a two-color pH indicator (1). The pH of the trap. The unit is loosely packed with 16-mesh activated
final solution is adjusted to the desired value by the addition of coconut charcoal and glass wool to prevent moisture entrain-
prescribed amounts of 3 N H PO to the pararosaniline reagent ment. The charcoal should be changed weekly.
3 4
(4). 7.1.5 Filter, membrane, of 0.8 to 2.0-μm porosity, with filter
4.2 Automated Method II is based on Manual Method A. holder.
7.1.6 Pump, capable of maintaining a vacuum greater than
5. Significance and Use
70 kPa (0.7 atm) at the specified flow rate.
5.1 Sulfur dioxide is a major air pollutant, commonly
7.1.7 Flow Control and Measurement Devices:
formed by the combustion of sulfur-bearing fuels. The Envi-
7.1.7.1 Flow Control Device—Any device capable of main-
ronmental Protection Agency (EPA) has set primary and
taining a constant flow rate (62%) can be used. For 1-h
secondary air quality standards (6) that are designed to protect
sampling (0.5 L/min), a 23-gage hypodermic needle 16 mm
the public health and welfare.
long (10) or a needle valve is suggested. For 24-h sampling
5.2 The Occupational Safety and Health Administration
(0.2 L/min), a 27-gage hypodermic needle 10 mm long is
(OSHA) has promulgated exposure limits for sulfur dioxide in
suggested. In either case, protect the needle valve or critical
workplace atmospheres (7).
orifice from particulate matter and moisture entrainment.
5.3 These methods have been found satisfactory for mea-
7.1.8 Thermometer—ASTM Thermometer 33C, meeting
suring sulfur dioxide in ambient and workplace atmospheres
the requirements of Specification E 1 will meet the require-
over the ranges pertinent in 5.1 and 5.2.
ments of most applications in this method.
5.4 The Manual Method A has been designed to correspond
7.1.9 Barograph or Barometer, capable of measuring atmo-
to the EPA-Designated Reference Method (6) for the determi-
spheric pressure to 60.5 kPa (5 torr).
nation of sulfur dioxide, and Automated Methods I and II have
7.1.10 The arrangement of the component parts for sam-
been designed to correspond to the EPA-designed equivalent
pling is shown in Fig. 1. See Practice D 1605 for discussion of
methods (8, 9).
this apparatus.
7.2 For Manual Methods A and B:
6. Interferences
7.2.1 Spectrophotometer or Colorimeter—The instrument
6.1 The interferences of oxides of nitrogen are eliminated
shall be suitable for measurement of color at 548 nm for
by sulfamic acid (4, 5) of ozone by time delay (4) and of heavy
Method A or 575 nm for Method B. With Method A, reagent
metals by EDTA and phosphoric acid (3, 4). At least 60 μg of
blank problems may result with spectrophotometers or colo-
Fe(III), 10 μg of Mn(II), and 10 μg of Cr(III) in 10 mL of
rimeters having a spectral bandwidth greater than 10 nm. The
absorbing reagent can be tolerated in the procedure. No
wavelength calibration of the spectrophotometer shall be
significant interference was found with 10 μg of Cu(II) and 22
verified in accordance with Practice E 275. The optical cell
μg of V(V).
shall have a minimum path length of 10 mm.
7.2.2 Constant-Temperature Bath, capable of controlling
7. Apparatus
temperature to 62°C.
7.1 For Sampling:
7.3 Automated Methods I and II—The automated analytical
7.1.1 Absorber, 1-h Sampling—An all-glass midget im-
system will generally consist of a series of modular units that
pinger having a 25-mm outside diameter, a total capacity of 30
will perform the functions of feeding samples to the system by
mL, and a 1-mm diameter orifice having a clearance from the
means of a turntable, a pump to move the sample from the
bottom of the impinger of 4 6 1 mm. An impinger meeting
turntable to the analytical module and from the analytical
these specifications is commercially available from a number
module to a detection device such as a colorimeter. The pump
of manufacturers.
also provides the means of adding reagents to the sample to
7.1.2 Absorber, 24-h Sampling—A glass or polypropylene
develop a color, adjust the pH, or otherwise condition the
absorption tube approximately 30 mm in diameter and 160 mm
sample for the analytical finish. A recorder or a printout device
The boldface numbers in parentheses refer to the list of references at the end of
this standard. Gelman 37-mm in-line filters have been found satisfactory for this purpose.
D 2914
FIG. 1 Sampling System
is used to record the data or the signal that is generated by the flow rates are obtained by selecting pump tubing of the proper
detection device. There are several pieces of equipment avail- inside diameter. Deviation from these flow rates is acceptable
able to perform these functions. Two such systems will be only to the extent that a proper calibration curve and acceptable
presented, one of which is an older system and is designated as quality control checks are obtained.
Method I. The other is a newer system and is designated as 7.3.1.6 Mixing Coils and Time Delay Coils, as shown in
Method II. Table 2.
7.3.1 Automated System for Method I (see Fig. 2) consists 7.3.1.7 Aperture—A No. 4 sample aperture and a No. 1
of the following: reference aperture shall be normally used. Some other combi-
7.3.1.1 Turntable, set for 30 samples per hour and a 1:4 nation of apertures can be used if the baseline cannot be
ratio of sample to wash time. obtained with the specified apertures.
7.3.1.2 Sample Cups, 10-mL capacity. 7.3.1.8 Colorimeter with a Phototube Colorimeter Con-
13 14
7.3.1.3 Pump, capable of maintaining the flow rates in trol, with proper filters for measurement of transmittance at
Table 1. Pump tubing shall be poly(vinyl chloride), or other 570 nm. Interference filters shall have a spectral bandwidth not
inert tubing for sample and reagent. greater than 20 nm. The filters shall be checked with an
7.3.1.4 Sampler Probe, made of polychlorotrifluoroethylene accurate spectrophotometer, at least quarterly, to assure maxi-
or glass. Because of the corrosive properties of the TCM mum transmittance at the specified wavelength.
absorbing reagent, no metal shall contact the sample solution. 7.3.1.9 Flow Cell, 50-mm tubular.
7.3.1.5 Pump Tubes—The pump tubes are such that sample 7.3.1.10 Voltage Stabilizer.
and reagent flow rates are as specified in Table 1. The different 7.3.1.11 Strip Chart Recorder.
7.3.2 Automated System for Method II (see Fig. 3) consists
of the following:
Technicon I Automated Analyzer System has been found satisfactory for
7.3.2.1 Sampler Turntable, set for 40 samples per hour and
Method I.
a 6:1 ratio of sample to wash time.
Technicon II Automated Analyzer System has been found satisfactory for
7.3.2.2 Sample Cups, 10-mL volume.
Method II.
7.3.2.3 Proportioning Pump, capable of maintaining the
The Technicon Sampler II Turntable has been found to be satisfactory for this
purpose.
The Technicon Proportioning Pump I has been found satisfactory for this
purpose. Technicon Part No. 199-A001-02 has been found satisfactory for this purpose.
D 2914
NOTE 1—The part numbers refer to Technicon parts that have been found satisfactory for this purpose.
FIG. 2 Method I Automated Sulfur Dioxide Analysys System
TABLE 1 Pump Tubes Flow Rates
7.3.2.5 Pump Tubes—The pump tubes are such that sample
Automated Method and reagent flow rates are as specified in Table 1. The different
Automated Method II
Pump Tube Reagent I Flow Rate, mL/
flow rates are obtained by selecting pump tubing of the proper
Flow Rate, mL/min
min
inside diameter. Deviation from these flow rates is acceptable
TCM 3.5 1.8
only to the extent that a proper calibration curve and acceptable
Sample 2.2 0.32
quality control checks are obtained.
Air 0.50 0.56
Sulfamic acid 0.28 0.32
7.3.2.6 Mixing Coils, as described in Table 2.
Formaldehyde 1.1 0.10
7.3.2.7 Heating Bath, 45°C heated coil, total volume 5.4
p-Rosaniline 0.80 0.16
Waste 2.0 0.60 mL.
7.3.2.8 Colorimeter and Voltage Stabilizer, with proper
filters for measurement of absorbance at 560 nm. Interference
TABLE 2 Coil Sizes
filters shall have a spectral bandwidth not greater than 20 nm.
Number of Internal
The filters shall be checked with an accurate spectrophotom-
A
Part Number Description Turns or Diame-
eter, at least quarterly, to assure maximum transmittance at the
Length ter or Volume
specified wavelength.
157-0251-01 Mixing Coil 10 turns 2 mm
7.3.2.9 Flow Cell, 15-mm long with an inside diameter of 2
157-0248-01 Mixing Coi
...
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