This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles

for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

Designation: D2913 − 20

Standard Test Method for

Mercaptan Content of the Atmosphere1
This standard is issued under the fixed designation D2913; 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 (´) indicates an editorial change since the last revision or reapproval.

1. Scope 2. Referenced Documents

1.1 This test method is for the measurement of mercaptans 2.1 ASTM Standards:3
(organic thiols) in the atmosphere at concentrations below 100 D1193 Specification for Reagent Water
parts per billion (ppb(v) = 195 µg/m3). For concentrations D1356 Terminology Relating to Sampling and Analysis of
above 100 ppb(v), the sampling period can be reduced or the Atmospheres
trapping liquid volume increased either before or after aspirat- D1357 Practice for Planning the Sampling of the Ambient
ing. (See Practice D1357 for sampling guidance.) The mini- Atmosphere
mum detectable amount of methyl mercaptan is 0.04 µg/mL D1914 Practice for Conversion Units and Factors Relating to
(1)2 in a final liquid volume of 25 mL. When sampling air at Sampling and Analysis of Atmospheres
the maximum recommended rate of 2 L/min for 2 h, the D2914 Test Methods for Sulfur Dioxide Content of the
minimum detectable mercaptan concentration is 1.0 ppb(v) Atmosphere (West-Gaeke Method)
(1.95 µg methyl mercaptan/m3 at 101.3 kPa (760 mm Hg) and D3195 Practice for Rotameter Calibration
25°C). This test method determines total mercaptans and does
iTeh Standards
D3249 Practice for General Ambient Air Analyzer Proce-
not differentiate among individual mercaptans, although it is dures
most sensitive to the lower molecular weight alkanethiols. D3609 Practice for Calibration Techniques Using Perme-
1.2 The values stated in (https://standards.iteh.ai)
SI units are to be regarded as ation Tubes
standard. No other units of measurement are included in this D3631 Test Methods for Measuring Surface Atmospheric
standard.
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1.3 This standard does not purport to address all of the
Pressure
E2251 Specification for Liquid-in-Glass ASTM Thermom-
eters with Low-Hazard Precision Liquids
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish ASTM D2913-20
appro-
3. Terminology
priate safety, health, and environmental practices and deter-
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mine the applicability of regulatory limitations prior to use. 3.1 Definitions—For definitions of terms used in this test
Specific precautionary statements are given in 8.7, 8.8, and method, refer to Terminology D1356.
Section 9.
1.4 This international standard was developed in accor- 4. Summary of Test Method
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the 4.1 This test method is intended for obtaining an integrated
Development of International Standards, Guides and Recom- sample over a selected time span (such as 2 h) either manually
mendations issued by the World Trade Organization Technical or in an automatic sequential sampler using 10 mL of absorp-
Barriers to Trade (TBT) Committee. tion liquid in a bubbler.
4.2 The absorption liquid is delivered to the laboratory for
colorimetric analysis by reaction between the collected mer-
1
This test method is under the jurisdiction of ASTM Committee D22 on Air captan and N,N-dimethyl-p-phenylenediamine.
Quality and is the direct responsibility of Subcommittee D22.03 on Ambient
Atmospheres and Source Emissions.
Current edition approved Sept. 1, 2020. Published September 2020. Originally
3
approved in 1970. Last previous edition approved in 2014 as D2913 – 14. DOI: For referenced ASTM standards, visit the ASTM website, www.astm.org, or
10.1520/D2913-20. contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
2
The boldface numbers in parentheses refer to a list of references at the end of Standards volume information, refer to the standard’s Document Summary page on
this standard. the ASTM website.

Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States

1
 D2913 − 20
5. Significance and Use 7. Apparatus
5.1 Mercaptans are odorous substances offensive at low 7.1 Sampling Apparatus:
concentrations and toxic at higher levels. They are emitted 7.1.1 Absorber—Midget bubbler with coarse porosity frit.
from geothermal sources, industrial processes, and food pro- 7.1.2 Air Sample Probe—TFE-fluorocarbon, polypropylene,
cessing facilities. Mercaptans at low concentrations are com- or glass tube with a polypropylene or glass funnel at the end.
monly added to natural gas and LP gases for safety purposes as 7.1.3 Moisture Trap-Glass, or polypropylene tube with a
well. two port closure. The entrance port of the closure is fitted with
tubing that extends to the bottom of the trap. The unit is loosely
6. Interferences packed with 16-mesh activated charcoal to prevent moisture
entrainment. The charcoal should be changed at least weekly
6.1 The N,N-dimethyl-p-phenylenediamine reaction is also and more frequently when sampling high humidity air.
used in the determination of other sulfur-containing com- 7.1.4 Filter—Membrane, of 0.8 to 2.0 µm porosity.
pounds including hydrogen sulfide and dimethyl disulfide (2). 7.1.5 Pump—Capable of maintaining a vacuum greater than
The potential for interference from these latter compounds is 70 kPA (0.7 atm) at the specified flowrate.
especially important, since all of these compounds commonly 7.1.6 Flow Control Device—A needle valve capable of
coexist in certain industrial emissions. Appropriate selection of maintaining a constant flow rate (62 %). Protect the needle
the color formation conditions and measurements of absor- valve from particulate matter and moisture entrainment.
bance at the specified wavelength will eliminate the potential 7.1.7 Flow meter, having a range of 0 to 2.5 L/min.
interference from hydrogen sulfide. 7.1.8 Thermometers—Precision digital thermometers based
6.2 Hydrogen sulfide, if present in the sampled air, may on resistance temperature detectors (RTDs), thermistors,
cause a turbidity in the sample absorbing solution. This thermocouples, or organic liquid-in-glass thermometers (such
precipitate must be filtered before proceeding with the analysis. as Thermometer S18C in Specification E2251) meeting the
One study showed that 100 µg of H2S gave a mercaptan color requirements of specific applications in this method may be
equivalent to 1.5 to 2.0 µg of mercaptan (3). Another study used.
7.1.9 Barograph or Barometer—Capable of measuring at-
iTeh Standards
reported no absorption at 500 nm in the presence of 150 µg of
hydrogen sulfide (4, 5). mospheric pressure to 60.5 kPa (4 Torr), meeting the require-
ments of Test Methods D3631.
(https://standards.iteh.ai)
6.3 Approximately equimolar response is obtained from the
hydrolysis products of dimethyl disulfide, the molar extinction
coefficient for the amine-mercaptan reaction product being
7.1.10 Stopwatch or timer, accurate to 61 s/24 h.
7.1.11 The arrangements of the component parts of sam-

Document reaction product Preview

3
pling is shown in Fig. 1a, Test Methods D2914.
4.4 × 10 , and the amine-dimethyl disulfide
3
being 5.16 × 10 (5). The interference due to dimethyl disulfide 7.2 Calibration Apparatus—A means of generating dy-
has been experimentally determined. Dimethyl disulfide con- namic standard atmospheres using a permeation device. Dilu-
centrations of 0.6 ppm(v) and 1.0 ppm(v) given anASTM tion air and excess dilution flow must be filtered through
D2913-20
equivalent
activated charcoal to prevent recirculating small quantities of
response as 0.4 ppm(v) and 0.8 ppm(v), respectively, of methyl
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mercaptan. 4 mercaptans. See Practice D3609 for details.
7.3 Colorimeter or Spectrophotometer, (at 500 nm)—Use
6.4 Sulfur dioxide up to 250 µg does not influence the color
2.5- or 5.0-cm path length to obtain adequate sensitivity.
development even when sampling a test atmosphere containing
300 ppm(v) of SO2. 8. Reagents and Materials
6.5 Nitrogen dioxide does not interfere up to 700 µg of NO2 8.1 Purity of Reagents—Reagent grade chemicals shall be
when sampling a test atmosphere containing 6 ppm mercap- used in all tests. All reagents shall conform to the specifications
tans. Higher concentrations of NO2 caused a positive interfer- of the Committee on Analytical Reagents of the American
ence when mercaptans were present, but no interference in the Chemical Society, where such specifications are available.5
absence of mercaptans. Such elevated NO2 concentrations are Other grades may be used, provided it is first ascertained that
not commonly encountered in ambient air except in the vicinity the reagent is of sufficiently high purity to permit its use
of an accidental spillage. without lessening the accuracy of the determination.
6.6 The supply of mercuric acetate must be free of mercu- 8.2 Purity of Water—Unless otherwise indicated, references
rous ion. If mercurous ion is present, turbidity will result when to water shall mean reagent water conforming to Specification
the chloride ion-containing reagents are added in the last step D1193.
of the analytical procedure. 8.3 Solutions should be refrigerated when not in use.

4 5
Supporting data giving the results of a laboratory examination of this method ACS Reagent Chemicals, Specifications and Procedures for Reagents and
by the National Council of the Paper Industry for Air and Stream Improvement Standard-Grade Reference Materials, American Chemical Society, Washington,
(NCASI) are available in special report No. 80-07, “A Laboratory Examination of DC. For suggestions on the testing of reagents not listed by the American Chemical
the Use of the ASTM/APHA. Spectrophotometric Method for the Measurement of Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset,
Methyl Mercaptan in Kraft Mill Workspace Atmospheres,” May 1980, NCASI, 260 U.K., and the United States Pharmacopeia and National Formulary, U.S. Pharma-
Madison Ave., New York, NY 10016. copeial Convention, Inc. (USPC), Rockville, MD.

2
 D2913 − 20
8.4 Amine-Hydrochloric Acid Solution, Stock—Dissolve 5.0 9. Safety Precautions
g of N,N-dimethyl- p-phenylenediamine hydrochloride (p- 9.1 Mercury—The absorbing solution contains mercury
aminodimethylaniline hydrochloride) in 1 L of concentrated salts, which are toxic. Precautions for its use are described in
hydrochloric acid (HCl). Refrigerate at approximately 10°C 8.7.
and protect from light. This solution is stable for at least 6
months. 9.2 Disposal procedures are described in Annex A3, Test
Methods D2914.
8.5 Reissner Solution—Dissolve 67.6 g of ferric chloride
hexahydrate (FeCl3·6H2O) in distilled water, dilute to 500 mL, 9.3 Compressed Gas Cylinders and Permeation Tubes—
and mix with 500 mL of nitric acid (HNO3) solution containing Permeation tubes and compressed gas standards should only be
72 mL of boiled concentrated nitric acid (sp gr 1.42). This handled in well ventilated locations. Improper handling of
solution is stable for at least 3 months. compressed gas cylinders can result in explosion. Rapid release
of inert gases can result in asphyxiation. Compressed air
8.6 Color-Developing Reagent—Mix 3 volumes of amine supports combustion.
solution and 1 volume of Reissner solution. Prepare this 9.3.1 Compressed gas cylinders may be used in this test
solution freshly for each set of determinations. method for preparation of reagents or standard atmospheres.
8.7 Absorbing Solution—Dissolve 50 g of mercuric acetate Precautions on methyl mercaptan cylinders are described in
Hg (CH3COO)2 in 400 mL of distilled water and add 25 mL of 8.8.
glacial acetic acid (CH3COOH). Dilute to 1 L. The mercuric 9.3.2 General safety precautions for handling and storing
acetate must be free of mercurous salts to prevent precipitation compressed gas cylinders are described in Practice D3249.
of mercurous chloride during color development. Reagent
grade mercuric acetate sometimes contains mercurous mer- 10. Sampling
cury. Determine the acceptability of each new bottle of 10.1 Sampling procedures are described for 2–h sampling
mercuric acetate by adding 3 mL of concentrated hydrochloric periods. Different sampling rates and sampling times may be
acid to 3 mL of the 5 % mercuric acetate. If the solution selected to suit specific requirements, but sample volume and
iTeh Standards
becomes cloudy, the mercuric acetate is not acceptable.
(Warning—The absorbing solution and mercury salts are
flow rates must be adjusted to maintain linearity between
absorbance and concentration over the dynamic range of the

(https://standards.iteh.ai)
toxic. Avoid contact with the skin and especially with the eyes. colorimetric procedure.
Avoid generating or breathing dust. Wash hands after use. Keep
away from food. Do not ingest.) 10.2 Measure the temperature of the atmosphere being

Document
8.8 Lead Methyl Mercaptide—Bubble tank methyl mercap- Preview
tan gas (CH SH) into 10 % lead acetate solution
sampled before and after sampling.
10.3 Measure the atmospheric pressure during sampling, in
3
accordance with Test Methods D3631.
Pb(CH3COO)2 in a fume hood (1). Collect the yellow crystals
by vacuum filtration, wash with distilled water, ASTM D2913-20
and dry
11. Calibration and Standardization
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overnight in a vacuum oven at 45°C. Store crystals in a
vacuum-sealed container in the dark. One mole of this mer- 11.1 Sampling Equipment—Calibrate the flow meter before
captide is equivalent to two moles of a mercaptan. Lead and after use in accordance with Practice D3195.
mercaptide may be purchased from commercial sources, if 11.1.1 The pressure drop of the flow meter must be main-
desired. (Warning— Methyl mercaptan gas is extremely toxic. tained the same during sampling as during calibration.
At high levels of exposure, the human olfactory sense may
11.2 Standard Atmospheres—See Practice D3609 for prepa-
become insensitive to its presence.)
ration of standard atmospheres using the calibration apparatus
8.9 Concentrated, Standard Lead Mercaptide Solution— and the permeation device.
Weigh out 156.6 mg of the crystalline lead mercaptide and 11.2.1 Calibrate the components of the calibration apparatus
make up to 100 mL with the 5 % mercuric acetate absorbing and the permeation device in accordance with Practice D3609
solution. This solution contains the equivalent of 500 µg of before and after use.
methyl mercaptan/mL.
11.3 Calibration Curve:
8.10 Diluted Mercaptan Solution, Standard—Dilute 2 mL of 11.3.1 Sample five standard atmospheres in accordance with
the concentrated standard solution to 100 mL with the 5 % Section 12.1. The mercaptan content of the standard atmo-
mercuric acetate absorbing solution. This solution contains the spheres shall be such that the intensities of the color of the
equivalent of 10 µg CH3SH/mL. resultant analyzed solutions shall be evenly spaced over the
dynamic range of the analytic procedure. One of the five
8.11 Methyl Mercaptan Permeation Device, with a perme-
standard atmospheres shall be a blank, generated by removing
ation rate appropriate to the dilution flow and concentrations
or bypassing the permeation device.
expected. For example, see the table below.
11.3.2 Analyze the solutions according to 12.2.
Concentrations Permeation Rate Required
11.3.3 Prepare a calibration curve of total mass of mercap-
10 ppb(v) @ 2 L/min 40 ng/min tan collected versus absorbance of developed color, using the
100 ppm(v) @ 1 L/min 200 ng/min least squares method.