ASTM D2913-96(2007)
(Test Method)Standard Test Method for Mercaptan Content of the Atmosphere
Standard Test Method for Mercaptan Content of the Atmosphere
SIGNIFICANCE AND USE
Mercaptans are odorous substances offensive at low concentrations and toxic at higher levels. They are emitted from geothermal sources, industrial processes, and food processing facilities.
SCOPE
1.1 This test method covers measurement of the concentration of mercaptans (organic thiols) in the atmosphere at concentrations below 100 parts per billion (ppb(v) = 195 μg/m3). For concentrations above 100 ppb(v) level, the sampling period can be reduced or the liquid volume increased either before or after aspirating. The minimum detectable amount of methyl mercaptan is 0.04 μg/mL (1) in a final liquid volume of 25 mL. When sampling air at the maximum recommended rate of 2 L/min for 2 h, the minimum detectable mercaptan concentration is 1.0 ppb(v) (1.95 μg methyl mercaptan/m3 at 101.3 kPa (760 mm Hg) and 25°C). This test method determines total mercaptans and does not differentiate among individual mercaptans, although it is most sensitive to the lower molecular weight alkanethiols.
1.2 The values stated in SI units are to be regarded as the standard.
1.3 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. Specific precautionary statements are given in 8.7, 8.8, and Section 9.
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Designation: D2913 − 96(Reapproved 2007)
Standard Test Method for
Mercaptan Content of the Atmosphere
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.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope D1914PracticeforConversionUnitsandFactorsRelatingto
Sampling and Analysis of Atmospheres
1.1 This test method covers measurement of the concentra-
D2914Test Methods for Sulfur Dioxide Content of the
tion of mercaptans (organic thiols) in the atmosphere at
Atmosphere (West-Gaeke Method)
concentrations below 100 parts per billion (ppb(v) = 195
3 D3195Practice for Rotameter Calibration
µg/m ). For concentrations above 100 ppb(v) level, the sam-
D3249Practice for General Ambient Air Analyzer Proce-
pling period can be reduced or the liquid volume increased
dures
either before or after aspirating. The minimum detectable
2 D3609Practice for Calibration Techniques Using Perme-
amount of methyl mercaptan is 0.04 µg/mL (1) in a final
ation Tubes
liquid volume of 25 mL. When sampling air at the maximum
D3631Test Methods for Measuring Surface Atmospheric
recommended rate of 2 L/min for 2 h, the minimum detectable
Pressure
mercaptan concentration is 1.0 ppb(v) (1.95 µg methyl
3 E1Specification for ASTM Liquid-in-Glass Thermometers
mercaptan/m at 101.3 kPa (760 mm Hg) and 25°C). This test
method determines total mercaptans and does not differentiate
3. Terminology
among individual mercaptans, although it is most sensitive to
3.1 Definitions—For definitions of terms used in this test
the lower molecular weight alkanethiols.
method, refer to Terminology D1356.
1.2 The values stated in SI units are to be regarded as the
4. Summary of Test Method
standard.
4.1 This test method is intended for obtaining an integrated
1.3 This standard does not purport to address all of the
sample over a selected time span (such as 2 h) either manually
safety concerns, if any, associated with its use. It is the
or in an automatic sequential sampler using 10 mL of absorp-
responsibility of the user of this standard to establish appro-
tion liquid in a bubbler.
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use. Specific precau-
4.2 The absorption liquid is delivered to the laboratory for
tionary statements are given in 8.7, 8.8, and Section 9.
colorimetric analysis by reaction between the collected mer-
captan and N,N-dimethyl-p-phenylenediamine.
2. Referenced Documents
5. Significance and Use
2.1 ASTM Standards:
5.1 Mercaptans are odorous substances offensive at low
D1193Specification for Reagent Water
concentrations and toxic at higher levels. They are emitted
D1356Terminology Relating to Sampling and Analysis of
from geothermal sources, industrial processes, and food pro-
Atmospheres
cessing facilities.
D1357Practice for Planning the Sampling of the Ambient
Atmosphere
6. Interferences
6.1 The N,N-dimethyl-p-phenylenediamine reaction is also
suitable for the determination of other sulfur-containing com-
This test method is under the jurisdiction of ASTM Committee D22 on Air
pounds including hydrogen sulfide and dimethyl disulfide (2).
Qualityand is the direct responsibility of Subcommittee D22.03 on Ambient
The potential for interference from these latter compounds is
Atmospheres and Source Emissions.
especially important, since all of these compounds commonly
Current edition approved April 1, 2007. Published May 2007. Originally
´1
approved in 1970. Last previous edition approved in 2001 as D2913-96(2001) .
coexistincertainindustrialemissions.Appropriateselectionof
DOI: 10.1520/D2913-96R07.
the color formation conditions and measurements of absor-
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
bance at the specified wavelength will eliminate the potential
this test method.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or interference from hydrogen sulfide.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
6.2 Hydrogen sulfide, if present in the sampled air, may
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. cause a turbidity in the sample absorbing solution. This
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D2913 − 96 (2007)
precipitatemustbefilteredbeforeproceedingwiththeanalysis. 7.1.9 Barograph or Barometer—Capable of measuring at-
One study showed that 100 µg of H S gave a mercaptan color mospheric pressure to 60.5 kPa (4 Torr), meeting the require-
equivalent to 1.5 to 2.0 µg of mercaptan (3). Another study ments of Test Methods D3631.
reported no absorption at 500 nm in the presence of 150 µg of 7.1.10 Stopwatch or timer, accurate to 61 s/24 h.
hydrogen sulfide (4, 5). 7.1.11 The arrangements of the component parts of sam-
pling is shown in Fig. 1a, Test Methods D2914.
6.3 Approximately equimolar response is obtained from the
7.2 Calibration Apparatus—A means of generating dy-
hydrolysis products of dimethyl disulfide, the molar extinction
coefficient for the amine-mercaptan reaction product being namic standard atmospheres using a permeation device. Dilu-
tion air and excess dilution flow must be filtered through
4.4×10 , and the amine-dimethyl disulfide reaction product
being5.16×10 (5).Theinterferenceduetodimethyldisulfide activated charcoal to prevent recirculating small quantities of
mercaptans. See Practice D3609 for details.
has been experimentally determined. Dimethyl disulfide con-
centrations of 0.6 ppm(v) and 1.0 ppm(v) given an equivalent
7.3 Colorimeter or Spectrophotometer, (at 500 nm)—Use
responseas0.4ppm(v)and0.8ppm(v),respectively,ofmethyl
2.5- or 5.0-cm path length to obtain adequate sensitivity.
mercaptan.
8. Reagents and Materials
6.4 Sulfur dioxide up to 250 µg does not influence the color
developmentevenwhensamplingatestatmospherecontaining
8.1 Purity of Reagents—Reagent grade chemicals shall be
300 ppm(v) of SO .
2 usedinalltests.Allreagentsshallconformtothespecifications
of the Committee on Analytical Reagents of the American
6.5 Nitrogendioxidedoesnotinterfereupto700µgofNO
Chemical Society, where such specifications are available.
when sampling a test atmosphere containing 6 ppm. Higher
Other grades may be used, provided it is first ascertained that
concentrations of NO caused a positive interference when
the reagent is of sufficiently high purity to permit its use
mercaptans were present, but no interference in the absence of
without lessening the accuracy of the determination.
mercaptans. Such elevated NO concentrations are unrealistic
and would not be encountered in the ambient air except in the 8.2 Purity of Water—Unless otherwise indicated, references
vicinity of an accidental spillage.
to water shall mean referee reagent water conforming to
Specification D1193.
6.6 The supply of mercuric acetate must be free of mercu-
rous ion. If mercurous ion is present, turbidity will result when 8.3 Solutions should be refrigerated when not in use.
the chloride ion-containing reagents are added in the last step
8.4 Amine-Hydrochloric Acid Solution, Stock—Dissolve 5.0
of the analytical procedure.
gof N,N-dimethyl- p-phenylenediamine hydrochloride (p-
aminodimethylaniline hydrochloride) in 1 L of concentrated
7. Apparatus
hydrochloric acid (HCL). Refrigerate and protect from light.
This solution is stable for at least 6 months.
7.1 Sampling Apparatus:
7.1.1 Absorber—Midget bubbler with coarse porosity frit.
8.5 Reissner Solution—Dissolve 67.6 g of ferric chloride
7.1.2 Air Sample Probe—TFE-fluorocarbon,polypropylene,
hexahydrate (FeCl ·6H O) in distilled water, dilute to 500 mL,
3 2
or glass tube with a polypropylene or glass funnel at the end.
andmixwith500mLofnitricacid(HNO )solutioncontaining
7.1.3 Moisture Trap-Glass, or polypropylene tube with a
72 mL of boiled concentrated nitric acid (sp gr 1.42). This
two port closure.The entrance port of the closure is fitted with
solution is stable.
tubingthatextendstothebottomofthetrap.Theunitisloosely
8.6 Color-Developing Reagent—Mix 3 volumes of amine
packed with 16-mesh activated charcoal to prevent moisture
solution and 1 volume of Reissner solution. Prepare this
entrainment. The charcoal should be changed weekly.
solution freshly for each set of determinations.
7.1.4 Filter—Membrane, of 0.8 to 2.0 µm porosity.
8.7 Absorbing Solution—Dissolve 50 g of mercuric acetate
7.1.5 Pump—Capableofmaintainingavacuumgreaterthan
Hg(CH COO) in400mLofdistilledwaterandadd25mLof
3 2
70 kPA (0.7 atm) at the specified flowrate.
glacial acetic acid (CH COOH). Dilute to 1 L. The mercuric
7.1.6 Flow Control Device—A needle valve capable of
acetatemustbefreeofmercuroussaltstopreventprecipitation
maintaining a constant flow rate (62%). Protect the needle
of mercurous chloride during color development. Reagent
valve from particulate matter and moisture entrainment.
grade mercuric acetate sometimes contains mercurous mer-
7.1.7 Flow meter, having a range of 0 to 2.5 L/min.
cury. Determine the acceptability of each new bottle of
7.1.8 Thermometers—ASTM Thermometer 33C, meeting
mercuric acetate by adding 3 mLof concentrated hydrochloric
the requirements of Specification E1, will be suitable for most
acid to 3 mL of the
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