ASTM D6228-98
(Test Method)Standard Test Method for Determination of Sulfur Compounds in Natural Gas and Gaseous Fuels by Gas Chromatography and Flame Photometric Detection
Standard Test Method for Determination of Sulfur Compounds in Natural Gas and Gaseous Fuels by Gas Chromatography and Flame Photometric Detection
SCOPE
1.1 This test method provides for the determination of individual volatile sulfur-containing compounds in gaseous fuels by gas chromatography (GC) with flame photometric detection (FPD). The detection range for sulfur compounds is from 20 to 20 000 picograms (pg) of sulfur. This is equivalent to 0.02 to 20 mg/m3 or 0.014 to 14 ppmv of sulfur based upon the analysis fo a 1-mL sample.
1.2 This test method describes a GC-FPD method using a specific capillary GC column. Other GC-FPD methods, with differences in GC column and equipment setup and operation, may be used as alternative methods for sulfur compound analysis with different range and precision, provided that appropriate separation of the sulfur compounds of interest can be achieved.
1.3 This test method does not intend to identify all individual sulfur species. Total sulfur content of samples can be estimated from the total of the individual compounds determined. Unknown compounds are calculated as monosulfur-containing compounds.
1.4 The values stated in SI units are to be regarded as standard. The values stated in inch-pound units are for information only.
1.5 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.
General Information
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Please contact ASTM International (www.astm.org) for the latest information.
Designation:D6228–98
Standard Test Method for
Determination of Sulfur Compounds in Natural Gas and
Gaseous Fuels by Gas Chromatography and Flame
Photometric Detection
This standard is issued under the fixed designation D 6228; 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 (ϵ) indicates an editorial change since the last revision or reapproval.
1. Scope D 3609 Practice for Calibration Techniques Using Perme-
ation Tubes
1.1 This test method provides for the determination of
D 4468 Test Method for Total Sulfur in Gaseous Fuels by
individual volatile sulfur-containing compounds in gaseous
Hydrogenolysis and Rateometric Colorimetry
fuels by gas chromatography (GC) with flame photometric
D 4626 Practice for Calculation of Gas Chromatographic
detection (FPD). The detection range for sulfur compounds is
Response Factors
from 20 to 20 000 picograms (pg) of sulfur. This is equivalent
D 5287 Practice forAutomatic Sampling of Gaseous Fuels
to 0.02 to 20 mg/m or 0.014 to 14 ppmv of sulfur based upon
D 5504 Test Method for Determination of Sulfur Com-
the analysis of a 1-mL sample.
pounds in Natural Gas and Gaseous Fuels by Gas Chro-
1.2 This test method describes a GC-FPD method using a
matography and Chemiluminescence Detection
specific capillary GC column. Other GC-FPD methods, with
E 840 Practice for Using Flame Photometric Detectors in
differences in GC column and equipment setup and operation,
Gas Chromatography
may be used as alternative methods for sulfur compound
2.2 EPA Standards:
analysis with different range and precision, provided that
EPA–15 Determination of Hydrogen Sulfide, Carbonyl Sul-
appropriate separation of the sulfur compounds of interest can
fide and Carbon Disulfide Emissions from Stationary
be achieved.
Sources, 40 CFR, Chapter 1, Part 60, Appendix A
1.3 This test method does not intend to identify all indi-
EPA–16 Semicontinuous Determination of Sulfur Emis-
vidual sulfur species. Total sulfur content of samples can be
sions from Stationary Sources, 40 CFR, Chapter 1, Part
estimated from the total of the individual compounds deter-
60, Appendix A
mined. Unknown compounds are calculated as monosulfur-
containing compounds.
3. Terminology
1.4 The values stated in SI units are to be regarded as
3.1 Abbreviations:
standard. The values stated in inch-pound units are for infor-
3.1.1 A common abbreviation of a hydrocarbon compound
mation only.
is to designate the number of carbon atoms in the compound.
1.5 This standard does not purport to address all the safety
A prefix is used to indicate the carbon chain form, while a
concerns, if any, associated with its use. It is the responsibility
subscript suffix denotes the number of carbon atoms, for
of the user of this standard to establish appropriate safety and
example, normal decane = n-C , isotetradecane = i-C .
10 14
health practices and determine the applicability of regulatory
3.1.2 Sulfur compounds commonly are referred to by their
limitations prior to use.
initials, chemical or formula, for example, methyl mercaptan =
2. Referenced Documents MeSH, dimethyl sulfide = DMS, carbonyl sulfide = COS,
di-t-butyl trisulfide = DtB-TS, and tetrahydothiophene = THT
2.1 ASTM Standards:
or thiophane.
D 1072 Test Method for Total Sulfur in Fuel Gases
D 1265 Practice for Sampling Liquefied Petroleum (LP)
4. Summary of Test Method
Gases–Manual Method
4.1 Sulfur analysis ideally is performed on-site to eliminate
D 1945 Test Method for Analysis of Natural Gas by Gas
potential sample deterioration during storage. The reactive
Chromatography
nature of sulfur components may pose problems both in
sampling and analysis. Samples should be collected and stored
This test method is under the jurisdiction ofASTM Committee D-3 on Gaseous
Fuels and is the direct responsibility of Subcommittee D03.05 on Determination of
Special Constituents of Gaseous Fuels.
Current edition approved March 10, 1998. Published May 1998. Annual Book of ASTM Standards, Vol 11.03.
2 5
Annual Book of ASTM Standards, Vol 05.05. Annual Book of ASTM Standards, Vol 05.02.
3 6
Annual Book of ASTM Standards, Vol 05.01. Annual Book of ASTM Standards, Vol 14.02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Please contact ASTM International (www.astm.org) for the latest information.
D6228–98
in containers that are nonreactive to sulfur compounds, such as 6. Apparatus
Tedlar bags. Sample containers should be filled and purged at
6.1 Chromatograph—Any gas chromatograph that has the
least three times to ensure representative sampling. Laboratory
following performance characteristics can be used.
equipment also must be inert, well conditioned, and passivated
6.1.1 Sample Inlet System—Gas samples are introduced to
with a gas containing the sulfur compounds of interest to
the gas chromatograph using an automated or manually oper-
ensure reliable results. Frequent calibration and daily verifica-
ated stainless steel gas sampling valve enclosed in a heated
tion of calibration curve using stable standards are required.
valve oven, which must be capable of operating continuously
Samples should be analyzed within 24 h of collection to
at a temperature of 50°C above the temperature at which the
minimize sample deterioration. If the stability of analyzed
gaswassampled.TFE-fluorocarbontubingmadeoffluorinated
sulfur components is proved experimentally, the time between
ethylene propylene (FEP), 316 stainless steel tubing, or other
collection and analysis may be lengthened.
tubing made of nonpermeable, nonsorbing, and nonreactive
4.2 A 1-mL sample of the fuel gas is injected into a gas
materials, as short as possible and heat traced at the same
chromatograph where it is passed through a 60-m, 0.53-mm
temperature, should be used for transferring the sample from a
inside diameter (ID), thick film, methyl silicone liquid phase,
sample container to the gas-sampling valve. A 1.0-mL sam-
open tubular partitioning column, or a similar column capable
pling loop made of nonreactive materials, such as deactivated
of separating sulfur components.
fused silica or 316 stainless steel is used to avoid possible
4.3 Flame Photometric Detectors—When combusted in a
decomposition of reactive sulfur species. Other size fixed-
hydrogen-rich flame, sulfur compounds emit light energy
volumesamplingloopsmaybeusedfordifferentconcentration
characteristic to all sulfur species. The light is detected by a
ranges. A 1- to 2-m section of deactivated precolumn attached
photomultipliertube(PMT).ThePMTresponseisproportional
to the front of the analytical column is recommended. The
to the concentration or the amount of sulfur. All sulfur
precolumn is connected directly to the gas sampling valve for
compounds including sulfur odorants can be detected by this
on-column injection. The inlet system must be well condi-
technique.
tioned and evaluated frequently for compatibility with trace
4.4 Other Detectors—This test method is written primarily
quantities of reactive sulfur compounds, such as tert-butyl
for the flame photometric detector. The same gas chromato-
mercaptan.
graphic (GC) method can be used with other sulfur-specific
6.1.2 Digital Pressure Transmitter—A calibrated stainless
detectors provided they have sufficient sensitivity and selectiv-
steel pressure/vacuum transducer with a digital readout may be
ity to all sulfur compounds of interest in the required measure-
equipped to allow sampling at different pressures to generate
ment range.
calibration curves.
4.5 Other GC Test Methods—The GC test methods using
6.1.3 Column Temperature Programmer—The chromato-
sulfur chemiluminescence, reductive rateometric, and electro-
graph must be capable of linear programmed temperature
chemical detectors are available or under development.
operation over a range from 30 to 200°C, in programmed rate
settings of 0.1 to 30°C/min. The programming rate must be
5. Significance and Use
sufficiently reproducible to obtain retention time repeatability
5.1 Many sources of natural gas and petroleum gases
of 0.05 min (3 s).
containvaryingamountsandtypesofsulfurcompounds,which
6.1.4 Carrier and Detector Gas Control—Constant flow
are odorous, corrosive to equipment, and can inhibit or destroy
control of carrier and detector gases is critical to optimum and
catalystsusedingasprocessing.Theiraccuratemeasurementis
consistent analytical performance. Control is best provided by
essential to gas processing, operation, and utilization.
the use of pressure regulators and fixed flow restrictors. The
5.2 Small amounts, typically, 1 to 4 ppmv of sulfur odorant
gas flow rate is measured by any appropriate means and the
compounds, are added to natural gas and liquefied petroleum
required gas flow indicated by the use of a pressure gage. Mass
(LP) gases for safety purposes. Some odorant compounds can
flow controllers, capable of maintaining gas flow constant to
be reactive and may be oxidized, forming more stable com-
61 % at the required flow rates also can be used. The supply
pounds having lower odor thresholds. These gaseous fuels are
pressure of the gas delivered to the gas chromatograph must be
analyzed for sulfur odorants to help ensure appropriate odorant
at least 69 kPa (10 psi) greater than the regulated gas at the
levels for safety.
instrument to compensate for the system back pressure. In
5.3 This test method offers a technique to determine indi-
general, a supply pressure of 552 kPa (80 psig) will be
vidualsulfurspeciesingaseousfuelandthetotalsulfurcontent
satisfactory.
by calculation. Gas chromatography is used commonly and
6.1.5 Detector—A flame photometric detector calibrated in
extensively to determine other components in gaseous fuels
the sulfur-specific mode is used for this test method. Other
including fixed gas and organic components (see Test Method
detectors as mentioned in 4.4 will not be covered in this test
D 1945D 1945). This test method dictates the use of a specific
method. This detector may be obtained from various manufac-
GC technique with one of the more common detectors for
turers; however, there are variations in design. The pulsed
measurement.
flame photometric detector (PFPD) is one of the new FPD
designs. The pressure and flow rate of the hydrogen and air
gases used in the detector may be different. The selection of
which detector to use should be based on its performance for
Registered trademark. Available from DuPont de Nemours, E. I., & Co., Inc.,
Barley Mill Plaza, Bldg. 10, Wilmington, DE 19880–0010. the intended application. The detector should be set according
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Please contact ASTM International (www.astm.org) for the latest information.
D6228–98
to the manufacturer’s specifications and tuned to the best above a level of 0.1 % of the permeated sulfur species. See
performance of sensitivity and selectivity as needed. Practice D 3609D 3609.
7.2 Compressed Cylinder Gas Standards—As an alterna-
6.1.5.1 When sulfur-containing compounds are burned in a
tive, blended gaseous sulfur standards may be used if a means
hydrogen-rich flame, they quantitatively produce a S * species
to ensure accuracy and stability of the mixture is available.
in an excited state (Eq 1 and Eq 2). The light emitted from this
These mixtures can be a source of error if their stability during
species is detected by a photomultiplier tube (PMT) (Eq 3). A
storage cannot be guaranteed.
393-nm bandpass optical filter normally is used to enhance the
selectivityofdetection.Theselectivitynormallyisabout10 to
NOTE 1—Warning: Sulfur compounds may be flammable and harmful
1 by mass of sulfur to mass of carbon.
or fatal if ingested or inhaled.
RS 1 O → n CO 1 SO (1)
2 2 2
7.3 Carrier Gas—Helium or nitrogen of high purity
2SO 14H →4H O 1 S * (2) (99.999 % min purity) (Warning—See Note 2). Additional
2 2 2 2
purification is recommended by the use of molecular sieves or
S *→ S 1 hn (3)
2 2
other suitable agents to remove water, oxygen, and hydrocar-
where:
bons.Available pressure must be sufficient to ensure a constant
hν = emitted light energy.
carrier gas flow rate (see 6.1.4).
6.1.5.2 The intensity of light is not linear with the sulfur
NOTE 2—Warning: Helium and nitrogen used are compressed gases
concentration but is proportional approximately to the square
under high pressure.
of the sulfur concentration. The relationship between the FPD
7.4 Hydrogen—Hydrogen of high purity (99.999 % min
response (R ) and the sulfur concentration (S) is given by Eq
D
purity) is used as fuel for the flame photometric detector (FPD)
4 and Eq 5. The n-factor usually is less than 2.0.
(Warning—See Note 3).
n
R a [S# (4)
D
NOTE 3—Warning: Hydrogen is an extremely flammable gas under
Log [S# a 1/n Log R (5)
high pressure.
where:
7.5 Air—High-purity (99.999 % min purity) compressed air
n = exponential factor (1.7 to 2.0).
is used as the oxidant for the flame photometric detector (FPD)
6.1.5.3 The linear calibration curve can be made using a (Warning—See Note 4).
log-log plot. Some instruments use an electronic linearizer to
NOTE 4—Warning: Compressed air is a gas under high pressure that
produce a signal with direct linear response. The dynamic
supports combustion.
range of this linear relationship is about 1 3 10 .
8. Preparation of Apparatus and Calibration
6.2 Column—A 60- by 0.53-m ID fused silica open tubular
column containing a 5-µm film thickness of bonded methyl
8.1 Chromatograph—Place in service in accordance with
silicone liquid phase is used. The column shall provide
the manufacturer’s instructions. Typical operating conditions
adequate retention and resolution characteristics under the
are shown in Table 1.
experimental conditions described in 7.3. Other columns,
8.2 FPD—Place the detector in service in accordance with
which can provide equivalent separation can be used, as well.
the manufacturer’s instructions. Hydrogen and air flows are
6.3 Data Acquisition:
critical and must be adjusted properly in accordance with the
instruction furnished by the manufacturer. With the FPD flame
6.3.1 Recorder—A 0- to 1-mV range recording potentiom-
eter or equivalent, with a full-scale response time of2sor less ignited, monitor the signal to verify compliance with the signal
noise and drift specified by the manufacturer. The FPD flame
can be used.
should be maintained to give consistent and optimum sensitiv-
6.3.2
...
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