ASTM D6228-19

Standard Test Method for Determination of Sulfur Compounds in Natural Gas and Gaseous Fuels by Gas Chromatography and Flame Photometric Detection

SIGNIFICANCE AND USE
5.1 Many sources of natural gas and petroleum gases contain varying amounts and types of sulfur compounds, which are odorous, corrosive to equipment, and can inhibit or destroy catalysts used in gas processing. Their accurate measurement is essential to gas processing, operation, and utilization.  
5.2 Small amounts, typically, 1 to 4 ppmv of sulfur odorant compounds, are added to natural gas and liquefied petroleum (LP) gases for safety purposes. Some odorant compounds can be reactive and may be oxidized, forming more stable compounds having lower odor thresholds. These gaseous fuels are analyzed for sulfur odorants to help ensure appropriate odorant levels for safety.  
5.3 This test method offers a technique to determine individual sulfur species in gaseous fuel and the total sulfur content by calculation. Gas chromatography is used commonly and extensively to determine other components in gaseous fuels including fixed gas and organic components (see Test Method D1945). This test method dictates the use of a specific GC technique with one of the more common detectors for measurement.
SCOPE
1.1 This test method covers the determination of individual volatile sulfur-containing compounds in gaseous fuels by gas chromatography (GC) with a flame photometric detector (FPD) or a pulsed flame photometric detector (PFPD). 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 of a 1 mL sample.  
1.2 This test method describes a GC method using capillary column chromatography with either an FPD or PFPD.  
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 given in parentheses after SI units are provided for information only and are not considered standard.  
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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.6 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.

General Information

• Status: Published
• Publication Date: 31-Mar-2019
• ICS: 71.040.50 - Physicochemical methods of analysis
• ICS: 75.160.10 - Solid fuels
• Technical Committee: D03 - Gaseous Fuels

Relations

• Refers: ASTM D1265-23a - Standard Practice for Sampling Liquefied Petroleum (LP) Gases, Manual Method
• Effective Date: 01-Dec-2023
• Refers: ASTM D4626-23 - Standard Practice for Calculation of Gas Chromatographic Response Factors
• Effective Date: 01-Oct-2023
• Refers: ASTM D4626-95(2019) - Standard Practice for Calculation of Gas Chromatographic Response Factors
• Effective Date: 01-Dec-2019
• Refers: ASTM D5287-08(2015) - Standard Practice for Automatic Sampling of Gaseous Fuels (Withdrawn 2024)
• Effective Date: 01-Jun-2015
• Refers: ASTM D4468-85(2011) - Standard Test Method for Total Sulfur in Gaseous Fuels by Hydrogenolysis and<br> Rateometric Colorimetry
• Effective Date: 01-Nov-2011
• Refers: ASTM D3609-00(2010) - Standard Practice for Calibration Techniques Using Permeation Tubes
• Effective Date: 01-Apr-2010
• Refers: ASTM D1945-03(2010) - Standard Test Method for Analysis of Natural Gas by Gas Chromatography
• Effective Date: 01-Jan-2010
• Refers: ASTM D5287-08 - Standard Practice for Automatic Sampling of Gaseous Fuels
• Effective Date: 01-Dec-2008
• Refers: ASTM D5504-08 - Standard Test Method for Determination of Sulfur Compounds in Natural Gas and Gaseous Fuels by Gas Chromatography and Chemiluminescence
• Effective Date: 15-Jun-2008
• Refers: ASTM D4468-85(2006) - Standard Test Method for Total Sulfur in Gaseous Fuels by Hydrogenolysis and Rateometric Colorimetry
• Effective Date: 01-Jun-2006
• Refers: ASTM D5504-01(2006) - Standard Test Method for Determination of Sulfur Compounds in Natural Gas and Gaseous Fuels by Gas Chromatography and Chemiluminescence
• Effective Date: 01-Jun-2006
• Refers: ASTM D3609-00(2005) - Standard Practice for Calibration Techniques Using Permeation Tubes
• Effective Date: 01-Oct-2005
• Refers: ASTM E840-95(2005) - Standard Practice for Using Flame Photometric Detectors in Gas Chromatography
• Effective Date: 01-Sep-2005
• Refers: ASTM D4626-95(2005) - Standard Practice for Calculation of Gas Chromatographic Response Factors
• Effective Date: 01-May-2005
• Refers: ASTM D1265-04a - Standard Practice for Sampling Liquefied Petroleum (LP) Gases (Manual Method)
• Effective Date: 01-Nov-2004

Overview

ASTM D6228-19 sets out the standard test method for determining individual volatile sulfur-containing compounds in natural gas and gaseous fuels using gas chromatography (GC) with a flame photometric detector (FPD) or pulsed flame photometric detector (PFPD). Accurate measurement of sulfur compounds is essential as they are often odorous, corrosive to equipment, and can destroy catalysts used in gas processing. Additionally, sulfur compounds are added to natural gas and liquefied petroleum gas (LPG) for safety "odorization." This standard is recognized internationally and aligns with the World Trade Organization (WTO) principles on standardization.

Key Topics

• Scope and Measurement Range

  • Covers the determination of individual sulfur compounds in gaseous fuels.
  • Applicable for detection of sulfur within 20 to 20,000 picograms (pg) of sulfur, equivalent to 0.02–20 mg/m³ or 0.014–14 ppmv (parts per million by volume) in a 1 mL sample.

• Analytical Technique

  • Utilizes capillary column gas chromatography with either FPD or PFPD detectors.
  • Capable of separating and quantifying sulfur compounds, including odorant species and total sulfur by calculation.

• Calibration and Quality Control

  • Requires frequent calibration and verification using either permeation tube standards or high-precision cylinder gas standards.
  • Instrument performance and detector calibration are critical for reliable results.

• Sample Handling and Preparation

  • Emphasizes minimizing sample deterioration, using non-reactive containers (such as Tedlar bags), and analyzing samples promptly, ideally within 24 hours of collection.

• Data Reporting

  • Individual sulfur compound concentrations and total sulfur content should be reported.
  • Ensures traceability, repeatability, and documentation, supporting process safety and regulatory compliance.

Applications

• Natural Gas Processing

  • Detection and quantification of sulfur compounds is critical for preventing equipment corrosion, catalyst poisoning, and meeting product specifications.

• Pipeline Safety

  • Helps verify the adequacy of sulfur-based odorants in natural gas and LPG for leak detection, crucial for public safety and regulatory compliance.

• Environmental Monitoring

  • Provides essential data for monitoring sulfur emissions and ensuring adherence to environmental regulations for gaseous fuels.

• Quality Control and Research

  • Supports laboratories and quality control units in the energy sector, enabling accurate determination of trace sulfur species for product certification or research.

• Regulatory Compliance

  • Used in conjunction with environmental and safety regulations to guarantee safe delivery and use of gaseous fuels.

Related Standards

ASTM D6228-19 references and complements several recognized standards and practices, including:

• ASTM D1945 - Test Method for Analysis of Natural Gas by Gas Chromatography: Offers general procedures for gas analysis.
• ASTM D1265 - Practice for Sampling Liquefied Petroleum (LP) Gases, Manual Method: Addresses sampling techniques.
• ASTM D3609 - Practice for Calibration Techniques Using Permeation Tubes: Pertains to preparation of gas standards.
• ASTM D4468 - Test Method for Total Sulfur in Gaseous Fuels by Hydrogenolysis and Rateometric Colorimetry.
• ASTM D5504 - Test Method for Determination of Sulfur Compounds in Natural Gas and Gaseous Fuels by Gas Chromatography and Chemiluminescence.
• ASTM E840 – Practice for Using Flame Photometric Detectors in Gas Chromatography.
• EPA Method 15 and Method 16 – Procedures for determination of hydrogen sulfide and other sulfur compounds in stationary source emissions.

Practical Value

Adoption of ASTM D6228-19 enables organizations to ensure reliable determination of sulfur compounds in natural gas and related fuels, supporting operational efficiency, process safety, and regulatory compliance. Its robust GC-FPD and GC-PFPD methodology allows for effective monitoring and quality assurance in the gas industry, from processing facilities to utilities and environmental compliance laboratories. This standard strengthens product quality, environmental stewardship, and public safety.

Keywords: ASTM D6228-19, sulfur compounds, natural gas analysis, gas chromatography, flame photometric detection, PFPD, sulfur odorants, gaseous fuels, sulfur testing, pipeline safety, gas processing standards.

Standards Content (Sample)

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: D6228 − 19
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 D6228; 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 covers the determination of individual 2.1 ASTM Standards:
volatile sulfur-containing compounds in gaseous fuels by gas D1265 Practice for Sampling Liquefied Petroleum (LP)
chromatography (GC) with a flame photometric detector (FPD) Gases, Manual Method
or a pulsed flame photometric detector (PFPD). The detection D1945 Test Method for Analysis of Natural Gas by Gas
range for sulfur compounds is from 20 to 20 000 picograms Chromatography
(pg) of sulfur. This is equivalent to 0.02 to 20 mg/m or 0.014 D3609 Practice for Calibration Techniques Using Perme-
to 14 ppmv of sulfur based upon the analysis of a 1 mL sample. ation Tubes
D4468 Test Method for Total Sulfur in Gaseous Fuels by
1.2 This test method describes a GC method using capillary
Hydrogenolysis and Rateometric Colorimetry
column chromatography with either an FPD or PFPD.
D4626 Practice for Calculation of Gas Chromatographic
1.3 This test method does not intend to identify all indi-
Response Factors
vidual sulfur species. Total sulfur content of samples can be
D5287 Practice for Automatic Sampling of Gaseous Fuels
estimated from the total of the individual compounds deter-
D5504 Test Method for Determination of Sulfur Compounds
mined. Unknown compounds are calculated as monosulfur-
in Natural Gas and Gaseous Fuels by Gas Chromatogra-
containing compounds.
phy and Chemiluminescence
1.4 The values stated in SI units are to be regarded as E840 Practice for Using Flame Photometric Detectors in Gas
standard. The values given in parentheses after SI units are Chromatography
2.2 EPA Standards:
provided for information only and are not considered standard.
EPA–15 Determination of Hydrogen Sulfide, Carbonyl Sul-
1.5 This standard does not purport to address all of the
fide and Carbon Disulfide Emissions from Stationary
safety concerns, if any, associated with its use. It is the
Sources, 40 CFR, Chapter 1, Part 60, Appendix A
responsibility of the user of this standard to establish appro-
EPA–16 Semicontinuous Determination of Sulfur Emissions
priate safety, health, and environmental practices and deter-
from Stationary Sources, 40 CFR, Chapter 1, Part 60,
mine the applicability of regulatory limitations prior to use.
Appendix A
1.6 This international standard was developed in accor-
dance with internationally recognized principles on standard-
3. Terminology
ization established in the Decision on Principles for the
3.1 Abbreviations:
Development of International Standards, Guides and Recom-
3.1.1 A common abbreviation of a hydrocarbon compound
mendations issued by the World Trade Organization Technical
is to designate the number of carbon atoms in the compound.
Barriers to Trade (TBT) Committee.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
This test method is under the jurisdiction of ASTM Committee D03 on Gaseous contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Fuels and is the direct responsibility of Subcommittee D03.06.01 on Analysis of Standards volume information, refer to the standard’s Document Summary page on
Major Constituents by Gas Chromatography. the ASTM website.
Current edition approved April 1, 2019. Published May 2019. Originally Available from United States Environmental Protection Agency (EPA), William
approved in 1998. Last previous edition approved in 2010 as D6228 – 10 which was Jefferson Clinton Bldg., 1200 Pennsylvania Ave., NW, Washington, DC 20460,
withdrawn January 2019 and reinstated in April 2019. DOI: 10.1520/D6228-19. http://www.epa.gov.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6228 − 19
A prefix is used to indicate the carbon chain form, while a 5.2 Small amounts, typically, 1 to 4 ppmv of sulfur odorant
subscript suffix denotes the number of carbon atoms, for compounds, are added to natural gas and liquefied petroleum
example, normal decane = n-C , isotetradecane = i-C .
(LP) gases for safety purposes. Some odorant compounds can
10 14
3.1.2 Sulfur compounds commonly are referred to by their be reactive and may be oxidized, forming more stable com-
initials, chemical or formula, for example, methyl mercaptan =
pounds having lower odor thresholds. These gaseous fuels are
MeSH, dimethyl sulfide = DMS, carbonyl sulfide = COS,
analyzed for sulfur odorants to help ensure appropriate odorant
di-t-butyl trisulfide = DtB-TS, and tetrahydothiophene = THT
levels for safety.
or thiophane.
5.3 This test method offers a technique to determine indi-
vidual sulfur species in gaseous fuel and the total sulfur content
4. Summary of Test Method
by calculation. Gas chromatography is used commonly and
4.1 Sample Collection—Sulfur analysis ideally is performed
extensively to determine other components in gaseous fuels
on-site to eliminate potential sample deterioration during
including fixed gas and organic components (see Test Method
storage. The reactive nature of sulfur components may pose
D1945). This test method dictates the use of a specific GC
problems both in sampling and analysis. Samples should be
technique with one of the more common detectors for mea-
collected and stored in containers that are nonreactive to sulfur
surement.
compounds, such as Tedlar bags. Sample containers should be
filled and purged at least three times to ensure representative
6. Apparatus
sampling. Laboratory equipment also must be inert, well
conditioned, and passivated with a gas containing the sulfur
6.1 Chromatograph—Any gas chromatograph that has the
compounds of interest to ensure reliable results. Frequent
following performance characteristics can be used.
calibration and daily verification of calibration curve using
6.1.1 Sample Inlet System—Gas samples are introduced to
stable standards are required. Samples should be analyzed
the gas chromatograph using an automated or manually oper-
within 24 h of collection to minimize sample deterioration. If
ated stainless steel gas sampling valve enclosed in a heated
the stability of analyzed sulfur components is proved
valve oven, which must be capable of operating continuously
experimentally, the time between collection and analysis may
at a temperature of 50 °C above the temperature at which the
be lengthened. See Practices D1265 and D5287.
gas was sampled. TFE-fluorocarbon tubing made of fluorinated
4.2 Sample Introduction—A 1 mL aliquot of the sample is ethylene propylene (FEP), passivated 316 stainless steel
injected into a gas chromatograph where it is passed through a
tubing, or other tubing made of nonpermeable, nonsorbing, and
capillary column capable of separating sulfur components.
nonreactive materials, as short as possible and heat traced at
the same temperature, should be used for transferring the
4.3 Flame Photometric Detectors (FPD and PFPD)—When
sample from a sample container to the gas-sampling valve. A
combusted in a hydrogen-rich flame, sulfur compounds emit
1.0 mL sampling loop made of nonreactive materials, such as
light energy characteristic to all sulfur species. The light is
deactivated fused silica or passivated 316 stainless steel is used
detected by a photomultiplier tube (PMT). The PMT response
to avoid possible decomposition of reactive sulfur species.
is proportional to the concentration or the amount of sulfur.
Other size fixed-volume sampling loops may be used for
Most sulfur compounds including sulfur odorants can be
different concentration ranges. The entire inlet system must be
detected by this technique.
well conditioned and evaluated frequently for compatability
4.4 Other Detectors—This test method is written primarily
with trace quantities of reactive sulfur compounds, such as
for the FPD and PFPD. Similar gas chromatographic (GC)
tert—butyl mercaptan.
method can be used with other sulfur-specific detectors pro-
6.1.1.1 On-Column Injections—For the FPD, a 1 to 2 m
vided they have sufficient sensitivity and selectivity to all
section of deactivated precolumn attached to the front of the
sulfur compounds of interest in the required measurement
analytical column is recommended. The precolumn is con-
range.
nected directly to the gas sampling valve for on-column
4.5 Other GC Test Methods—The GC test methods using
injection.
sulfur chemiluminescence (see Test Method D5504), reductive
6.1.1.2 Split Injections—For the PFPD, the column is con-
rateometric (see Test Method D4468), and electrochemical
nected to a heated flash vaporizing injector designed to provide
detectors are available or under development.
a linear sample split injection (for example, 50:1). The asso-
ciated carrier gas flow controls shall be of sufficient precision
5. Significance and Use
to provide reproducible column flows and split ratios in order
5.1 Many sources of natural gas and petroleum gases
to maintain analytical integrity.
contain varying amounts and types of sulfur compounds, which
6.1.2 Digital Pressure Transmitter—A calibrated stainless
are odorous, corrosive to equipment, and can inhibit or destroy
steel pressure/vacuum transducer with a digital readout may be
catalysts used in gas processing. Their accurate measurement is
equipped to allow sampling at different pressures to generate
essential to gas processing, operation, and utilization.
calibration curves.
6.1.3 Column Temperature Programmer—The chromato-
graph must be capable of linear programmed temperature
Registered trademark. Available from DuPont de Nemours, E. I., & Co., Inc.,
Barley Mill Plaza, Bldg. 10, Wilmington, DE 19880–0010. operation over a range from 30 to 200 °C, in programmed rate
D6228 − 19
settings of 0.1 to 30 °C ⁄min. The programming rate must be mately to the square of the sulfur concentration. The relation-
sufficiently reproducible to obtain retention time repeatability ship between the detector response (R ) and the sulfur con-
D
of 0.05 min (3 s). centration (S) is given by Eq 4 and Eq 5. The n-factor usually
6.1.4 Carrier and Detector Gas Control—Constant flow is less than 2.0.
control of carrier and detector gases is critical to optimum and
n
R α @S# (4)
D
consistent analytical performance. Control is best provided by
Log @S# α 1/n Log R (5)
the use of pressure regulators and fixed flow restrictors. The
gas flow rate is measured by any appropriate means and the
where:
required gas flow indicated by the use of a pressure gauge.
n = exponential factor (1.7 to 2.0).
Mass flow controllers, capable of maintaining gas flow con-
6.1.5.5 Linearity—The linear calibration curve can be made
stant to 61 % at the required flow rates also can be used. The
using a log-log plot. Some instruments provide optional
supply pressure of the gas delivered to the gas chromatograph
electronic algorithms to produce a signal with direct linear
must be at least 69 kPa (10 psi) greater than the regulated gas
response. The dynamic range of this linear relationship is about
at the instrument to compensate for the system back pressure.
1 × 10 .
In general, a supply pressure of 552 kPa (80 psig) will be
satisfactory.
6.2 Column—The capillary column shall be chosen to be
6.1.5 Detector—A flame photometric detector (FPD) or
compatible with the detector and detector gas flow rate
pulsed flame photometric dectector (PFPD) calibrated in the
requirements.
sulfur-specific mode is used for this test method. Other
6.2.1 FPD Column—A 60 m by 0.53 m ID fused silica open
detectors as mentioned in 4.4 will not be covered in this test
tubular column containing a 5 μm film thickness of bonded
method (see Practice E840). This detector may be obtained
methyl silicone liquid phase is used.
from various manufacturers; however, there are variations in
6.2.2 PFPD Column—A fused silica capillary column with
design. The pulsed flame photometric detector (PFPD) is one
0.32 mm ID or smaller and sufficient length (for example, 30 m
of the new FPD designs. The pressure and flow rate of the
or 60 m) and phase to separate the sulfur species is used.
hydrogen and air gases used in the detector may be different.
Helium carrier gas flow rate of 2.0 mL/minute or slower is
The selection of which detector to use should be based on its
used.
performance for the intended application. The detector should
6.2.3 The column shall provide adequate retention and
be set according to the manufacturer’s specifications and tuned
resolution characteristics under the experimental conditions
to the best performance of sensitivity and selectivity as needed.
described in 7.3. One example of a capillary column and
6.1.5.1 Principle of Operation—When sulfur-containing
operating conditions used with the FPD is shown in Table 1.
compounds are burned in a hydrogen-rich flame, they quanti-
Two examples of columns and operating conditions used with
tatively produce a S * species in an excited state (Eq 1 and Eq
the PFPD are shown in Table 2. Other columns, which can
2). The light emitted from this species is detected by a
provide equivalent separation, can be used as well.
photomultiplier tube (PMT) (Eq 3).
6.3 Data Acquisition:
6.1.5.2 Flame Photometric Detector (FPD)—In the FPD a
393 nm bandpass optical filter is normally used to enhance the 6.3.1 Recorder—A 0 to 1 mV range recording
selectivity of detection. The FPD selectivity normally is about potentiometer, or equivalent, with a full-scale response time of
10 to 1 by mass of sulfur to mass of carbon. 2 s or less can be used.
6.1.5.3 Pulsed Flame Photometric Detector (PFPD)—In the
6.3.2 Integrator—The use of an electronic integrating de-
PFPD the propagation of the flame produces gas phase
vice or computer is recommended. The device and software
reactions which result in light emissions with specific lumines-
must have the following capabilities:
cent spectra and lifetimes. The differences in specific emission
6.3.2.1 Graphic presentation of the chromatogram.
lifetimes combined with a broad-band optical filter and the
6.3.2.2 Digital display of chromatographic peak areas.
kinetics of the propagating flame, allow both time and wave-
6.3.2.3 Identification of peaks by retention time or relative
length information to be used to improve the PFPD’s selectiv-
retention time, or both.
ity and sensitivity. The PFPD selectivity relative to hydrocar-
bon is 10 or better, depending on gate settings and other
factors. Using gated electronics permit the acquisition of two,
simultaneous, mutually selective chromatograms (for example,
TABLE 1 GC-FPD Operating Parameters
sulfur and hydrocarbon).
Gas Sample Loop: 1.0 mL at 120 °C
RS1O →n CO 1SO (1)
Injection Type: On-column
2 2 2
Column: 60 m × 0.53 mm ID × 5 μ film, fused silica open tublar
2 SO 14 H →4 H O1S * (2)
2 2 2 2
column with bonded methyl silicone liquid phase
Carrier Gas: He at 11.0 mL/min or at a flow rate allowing CH
S *→S 1hν (3)
2 2
elutes at approximately 2.1 min
Column Oven: 30 °C hold 1.5 min, 15 °C ⁄min to 200 °C, hold 8 min,
where:
or as needed
hν = emitted light energy. Detector: Flame Photometric Detector (FPD) H /air ratio
specified by manufacturer, 250 °C, 20
6.1.5.4 Detector Response—The intensity of light is not
mL/min, helium makeup gas
linear with the sulfur concentration but is proportional approxi-
D6228 − 19
TABLE 2 GC-PFPD Operating Parameters
Parameter Column 1 Column 2
Gas Sample Loop: 1.0 mL at 150 °C 1.0 mL at 150 °C
Injection Type: Split; split ratio 50:1 Split: split ratio 50:1
Column: Agilent GS-GasPro PLOT column, 30 m× 0.32 mm ID Agilent J&W Select Low-Sulfur column,
60 m×0.32 mm ID
Carrier Gas: Helium at 2 mL/minute Helium at 2 mL/min
...