ASTM D8455-22

Standard Test Method for Speciated Siloxane GC-IMS Analyzer Based On-line for Siloxane and Trimethylsilanol Content of Gaseous Fuels

SIGNIFICANCE AND USE
5.1 Combustion of gaseous fuel containing significant siloxane concentrations results in conversion of these siloxanes to silicon dioxide (SiO2). This SiO2 accumulates on downstream equipment such as the interior of reciprocating engine cylinders (used for electricity generation and transportation applications), flame sensors, and condenser coils in residential/commercial furnaces, or post-combustion catalysts used for the removal of NO and NO2. In each of these cases, SiO2 compromises the performance of the equipment and may lead to eventual failure. Continuous measurement of siloxane concentrations enables a fuel producer to ensure their gas quality meets contractual obligations, regulatory requirements, pipeline injection tariff limits, and internal performance requirements. This method is intended to provide procedures for standardized start-up procedures, operating procedures, and quality assurance practices for on-line analysis of siloxanes using a GC-IMS analyzer.
SCOPE
1.1 This test method is for the determination of speciated siloxane concentrations in gaseous fuels using on-line Gas Chromatography Ion-Mobility Spectrometry (GC-IMS).  
1.2 Units—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.  
1.3 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.4 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: 30-Apr-2022
• ICS: 75.160.30 - Gaseous fuels
• Technical Committee: D03 - Gaseous Fuels
• Drafting Committee: D03.12 - On-Line/At-Line Analysis of Gaseous Fuels

Relations

• Refers: ASTM D6299-23a - Standard Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance
• Effective Date: 01-Dec-2023
• Refers: ASTM D4150-19 - Standard Terminology Relating to Gaseous Fuels
• Effective Date: 15-Dec-2019
• Refers: ASTM D6299-17b - Standard Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance
• Effective Date: 15-Dec-2017
• Refers: ASTM D6299-17a - Standard Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance
• Effective Date: 15-Nov-2017
• Refers: ASTM D6299-17 - Standard Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance
• Effective Date: 01-Jan-2017
• Refers: ASTM D4150-08(2016) - Standard Terminology Relating to Gaseous Fuels
• Effective Date: 01-Jul-2016
• Refers: ASTM D5287-08(2015) - Standard Practice for Automatic Sampling of Gaseous Fuels (Withdrawn 2024)
• Effective Date: 01-Jun-2015
• Refers: ASTM D3764-15e1 - Standard Practice for Validation of the Performance of Process Stream Analyzer Systems
• Effective Date: 01-Apr-2015
• Refers: ASTM D3764-15 - Standard Practice for Validation of the Performance of Process Stream Analyzer Systems
• Effective Date: 01-Apr-2015
• Refers: ASTM D6299-13e1 - Standard Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance
• Effective Date: 01-Oct-2013
• Refers: ASTM D6621-00(2012) - Standard Practice for Performance Testing of Process Analyzers for Aromatic Hydrocarbon Materials
• Effective Date: 01-Jun-2012
• Refers: ASTM D4298-04(2010) - Standard Guide for Intercomparing Permeation Tubes to Establish Traceability
• Effective Date: 01-Jul-2010
• Refers: ASTM D3609-00(2010) - Standard Practice for Calibration Techniques Using Permeation Tubes
• Effective Date: 01-Apr-2010
• Refers: ASTM D6299-10 - Standard Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance
• Effective Date: 01-Mar-2010
• Refers: ASTM D6299-10e2 - Standard Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance
• Effective Date: 01-Mar-2010

Overview

ASTM D8455-22 establishes a standard test method for the on-line determination of speciated siloxane and trimethylsilanol (TMSOL) concentrations in gaseous fuels using a Gas Chromatography Ion-Mobility Spectrometry (GC-IMS) analyzer. Reliable measurement of siloxanes in biogas, landfill gas, and other gaseous fuels is essential for ensuring equipment reliability, meeting gas quality specifications, fulfilling regulatory requirements, and maintaining operational performance. Combustion of siloxane-laden gas can produce silicon dioxide (SiO₂), a contaminant that accumulates on engine cylinders, sensors, heat exchangers, and catalyst beds, leading to equipment degradation or failure.

This standard outlines procedures for system start-up, operation, calibration, quality assurance, and maintenance requirements when using an on-line GC-IMS analyzer for continuous siloxane monitoring.

Key Topics

• Siloxane Analysis in Gaseous Fuels: Procedures for sampling and analyzing various siloxanes and TMSOL in gases such as biogas.
• GC-IMS Analyzer Operation: Guidance for system set-up, temperature control, sample handling, and measurement frequency to ensure accurate detection down to trace siloxane levels.
• Calibration and Quality Assurance: Recommendations for the use of reference standards, calibration gases, permeation tubes, and routine calibration verification to assure analytical integrity.
• Data Reporting: Standardized reporting formats, including measurement of individual siloxanes, total siloxane content, total SiO₂, and total silicon concentrations.
• System Installation and Maintenance: Requirements for sampling system materials, installation location, routine checks, and recommended system pre-tests and maintenance to achieve reliable results.
• Safety and Compliance: Emphasis on safe handling of compressed gases, heated components, and applicability of regulatory limitations.

Applications

This ASTM standard finds widespread application in the renewable energy and gas processing sectors:

• Biogas and Landfill Gas Plants: Continuous measurement of siloxane concentrations allows operators to monitor gas quality, prevent equipment fouling, and optimize gas cleaning systems.
• Power Generation: Monitoring siloxane content is critical for protecting reciprocating engines, turbines, and catalytic converters from SiO₂ buildup.
• Gas Utilities and Pipelines: Ensures that gas injected into pipelines meets tariff specifications and protects downstream infrastructure.
• Industrial and Commercial Furnaces: Helps maintain performance and lifespan of flame detectors, condensers, and other combustion devices using fuel gases.
• Environmental Compliance: Supports adherence to regulatory limits for siloxane emissions and gas compositions.

Routine application of ASTM D8455-22 can reduce maintenance costs, extend equipment life, and support contractual and regulatory compliance in facilities handling siloxane-prone gaseous fuels.

Related Standards

Adhering to ASTM D8455-22 may involve reference to several related standards, practices, and guides for comprehensive implementation and quality control:

• ASTM D3609: Calibration techniques using permeation tubes.
• ASTM D3764: Validation of the performance of process analyzer systems.
• ASTM D4150: Terminology relating to gaseous fuels.
• ASTM D4298: Guide for intercomparing permeation tubes to establish traceability.
• ASTM D5287: Practice for automatic sampling of gaseous fuels.
• ASTM D6299: Application of statistical quality assurance techniques for analytical measurement systems.
• ASTM D6621: Performance testing of process analyzers for aromatic hydrocarbon materials.
• ISO 10715: Natural gas - Sampling guidelines.

Practical Value

Implementing ASTM D8455-22 for on-line siloxane analysis using GC-IMS technology ensures accurate, real-time monitoring of gas quality, mitigates risk of equipment fouling from SiO₂, and helps maintain compliance with strict industry tariff and regulatory criteria. This standard is fundamental for gas producers, utility operators, and equipment manufacturers involved in fuel gas handling, treatment, and utilization. Proper adherence safeguards asset performance, reduces unplanned outages, and supports environmental and contractual obligations.

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: D8455 − 22
Standard Test Method for
Speciated Siloxane GC-IMS Analyzer Based On-line for
Siloxane and Trimethylsilanol Content of Gaseous Fuels
This standard is issued under the fixed designation D8455; 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 D6621 Practice for Performance Testing of Process Analyz-
ers for Aromatic Hydrocarbon Materials
1.1 This test method is for the determination of speciated
siloxane concentrations in gaseous fuels using on-line Gas
3. Terminology
Chromatography Ion-Mobility Spectrometry (GC-IMS).
3.1 Definitions—For definitions of terms used in D03 Gas-
1.2 Units—The values stated in SI units are to be regarded
eous Fuels standards, refer to Terminology D4150.
as standard. The values given in parentheses after SI units are
3.2 Definitions of Terms Specific to This Standard:
provided for information only and are not considered standard.
3.2.1 siloxanes, n—a functional group in organosilicon
1.3 This standard does not purport to address all of the
chemical family with the Si—O—Si linkage.
safety concerns, if any, associated with its use. It is the
3.2.1.1 Discussion—In this test method, “siloxanes” include
responsibility of the user of this standard to establish appro-
both “siloxanes and trimethylsilanol (TMSOL).”
priate safety, health, and environmental practices and deter-
3.3 Abbreviations—Several of the following abbreviations
mine the applicability of regulatory limitations prior to use.
are for common siloxanes that can be determined according to
1.4 This international standard was developed in accor-
this test method. This is not meant to construe that this test
dance with internationally recognized principles on standard-
method is constrained to determining only these substances.
ization established in the Decision on Principles for the
3.3.1 D3—Hexamethylcyclotrisiloxane
Development of International Standards, Guides and Recom-
3.3.2 D4—Octamethylcyclotetrasiloxane
mendations issued by the World Trade Organization Technical
3.3.3 D5—Decamethylcyclopentasiloxane
Barriers to Trade (TBT) Committee.
3.3.4 D6—Dodecamethylcyclohexasiloxane
3.3.5 DMS—data management system
2. Referenced Documents
3.3.6 GC-IMS—Gas Chromatography Ion-Mobility Spec-
2.1 ASTM Standards:
trometry
D3609 Practice for Calibration Techniques Using Perme-
3.3.7 L2—Hexamethyldisiloxane
ation Tubes
3.3.8 L3—Octamethyltrisiloxane
D3764 Practice forValidation of the Performance of Process
3.3.9 L4—Decamethyltetrasiloxane
Stream Analyzer Systems
3.3.10 L5—Dodecamethylpentasiloxane
D4150 Terminology Relating to Gaseous Fuels
3.3.11 NIST—National Institute of Standards and Technol-
D4298 Guide for Intercomparing Permeation Tubes to Es-
ogy
tablish Traceability
3.3.12 SOP—standard operating procedure
D5287 Practice for Automatic Sampling of Gaseous Fuels
3.3.13 TMSOL—Trimethylsilanol
D6299 Practice for Applying Statistical Quality Assurance
and Control Charting Techniques to Evaluate Analytical
4. Summary of Test Method
Measurement System Performance
4.1 A representative sample of a gaseous fuel is extracted
from a process pipe or pipeline and is transferred in a timely
manner through an appropriately designed sampling system to
ThistestmethodisunderthejurisdictionofASTMCommitteeD03onGaseous
the inlet of a siloxane analyzer.The sample is conditioned with
Fuels and is the direct responsibility of Subcommittee D03.12 on On-Line/At-Line
a minimum, preferably negligible, impact on the siloxane
Analysis of Gaseous Fuels.
content. The line used to transfer gas from the process pipe or
Current edition approved May 1, 2022. Published May 2022. DOI: 10.1520/
D8455-22.
pipeline to the instrument is heated to at least 65 °C to prevent
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
condensation of heavier siloxane species. The analyzer sample
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
loop is filled with a known volume of sample gas, after which
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. the contents of this sample loop are injected into a GC-IMS.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D8455 − 22
Excess process or pipeline sample is either vented to 5. Significance and Use
atmosphere, or returned to the process stream, depending on
5.1 Combustionofgaseousfuelcontainingsignificantsilox-
application, safety concerns, and regulatory requirements. If
ane concentrations results in conversion of these siloxanes to
the analyzer is installed inside a building and excess sample
silicon dioxide (SiO ). This SiO accumulates on downstream
2 2
gas is vented to atmosphere, the operator should run a
equipment such as the interior of reciprocating engine cylin-
ventilation line to a fume hood or outside.
ders (used for electricity generation and transportation
4.2 Sample gas is introduced to a gas chromatographic applications), flame sensors, and condenser coils in residential/
column, where the various siloxane species and other gas commercialfurnaces,orpost-combustioncatalystsusedforthe
constituents interact with the column material and are sepa- removal of NO and NO . In each of these cases, SiO
2 2
rated. compromises the performance of the equipment and may lead
to eventual failure. Continuous measurement of siloxane con-
4.3 Siloxanes and other gas constituents elute from the GC
centrations enables a fuel producer to ensure their gas quality
column, where they are introduced to the IMS drift chamber.A
+ meets contractual obligations, regulatory requirements, pipe-
low-radiation tritium source generates reactant ions H (H O) .
2 n
line injection tariff limits, and internal performance require-
These reactant ions chemically ionize compounds entering the
ments. This method is intended to provide procedures for
IMS cell, producing specific analyte ions. These ions are
standardized start-up procedures, operating procedures, and
released into the drift chamber at a defined frequency (gener-
quality assurance practices for on-line analysis of siloxanes
ally every 30 ms), then forced through the chamber via an
using a GC-IMS analyzer.
applied electric field. Simultaneously, nitrogen gas flows
through the drift cell in the opposite direction. As ions are
6. Apparatus
forced against the flow of nitrogen, they are separated by
6.1 Instrument (GC-IMS)—A gas chromatography column
chargeandgeometry,untiltheystrikeadetectorattheopposite
coupled to an ion mobility spectrometer drift cell and elec-
endofthedriftcell.Thisproducesachangeinelectricpotential
trometer. Table 2 summarizes the recommended analytical
(analyzerresponse)proportionaltothequantityofionsstriking
parameters for a GC-IMS configured to analyze siloxanes.
the detector. This two-stage separation produces a
Some GC-IMS analyzers or configurations may require differ-
3-dimensional chromatogram, as illustrated in the example
ent settings.
below. (See Fig. 1.)
6.1.1 The analyzer is typically configured to log IMS
NOTE 1—This illustration is meant for conceptual demonstration of a
temperature data and flag data as invalid (or prevent the
3D chromatogram; real chromatograms may include more analyte species
measurementaltogether)iftemperatureismeasuredoutsidethe
(such as TMSOL and D6) as well as non-target compounds.
acceptable range. The shutter releases ions into the drift cell
4.4 A GC-IMS configured to measure siloxanes in gaseous
every 30 ms, during which time the electrometer records the
fuels may measure silicon concentration down to the concen-
spectrum change in electric potential.
trations indicated in Table 1 using a 1 mLsample loop. This is
6.2 Sample Extraction—The location and orientation of
the maximum recommended sample loop volume.
sampling components are critical for ensuring that a represen-
4.5 Calibration, maintenance, quality assurance, and perfor-
tative sample is analyzed. The locations and orientation of
mance protocols provide a means to validate the analyzer
sampling components is expected to be selected based upon
operation and the generated results.
sound analytic and engineering considerations. Sampling prac-
4.6 The siloxane species analyzed by the GC-IMS include tices for gaseous fuels can be found in Practice D5287.Itisof
TMSOL, L2, L3, L4, L5, D3, D4, D5, and D6. critical importance that the sampling system be heated to at
FIG. 1 Conceptual Illustration of a 3D Chromatogram
D8455 − 22
TABLE 1 Siloxanes Limits of Quantification
Siloxanes and Silanols Limits of Quntification (LOQ) [1 mL Loop]
Species Silicon (Si) Silicon (Si) CAS#
(mg/m ) (ppb)
(TMSOL) Trimethylsilanol 0.006 1.6 1066-40-6
(L2) Hexamethyldisiloxane 0.007 1 107-46-0
(L3) Octamethyltrisiloxane 0.007 0.7 107-51-7
(L4) Decamethyltetrasiloxane 0.007 0.5 141-62-8
(L5) Dodecamethylpentasiloxane 0.018 1.1 141-63-9
(D3) Hexamethylcyclotrisiloxane 0.008 0.9 541-05-9
(D4) Octamethylcyclotetrasiloxane 0.008 0.7 556-67-2
(D5) Decamethylcyclopentasiloxane 0.008 0.5 541-02-6
(D6) Dodecamethylcyclohexasiloxane 0.019 1 540-97-64
TABLE 2 Recommended GC-IMS Operating Parameters
Parameter/Component Value/Details
Drift gas flow rate 150 mL ⁄min during analysis, 10 mL ⁄min in idle mode
Carrier gas flow rate 5 mL ⁄min until t=2 min, ramp to 15 mL ⁄min over 30 sec, maintain 15 mL for
remainder
GC Column temperature Isothermal - 80 °C ±0.1 °C
GC Column Low polarity, 30 m length x 0.32 mm ID
Injection Splitless; loop volume varies but 1 mL is suitable for most applications
IMS drift chamber length 98 mm
Electrical field strength 500 V ⁄cm
Scan collection time 30 ms
IMS temperature 65 °C ±1 °C
Ionization source Tritium
Drift chamber pressure Atmospheric (1 atm)
least 65 °C to prevent condensation of siloxane species, and all is delivered to the analyzer continuously, the analyzer only
sampling system components must be free of silicon-based withdraws a small subsample of the gas immediately before a
materials, such as lubricants. Sample gas should be passed measurement begins. This subsample is delivered to the GC
throughamembraneseparatortoremoveanyliquidsandsolids column through a sample loop with a known volume. The
present in the gas stream before the gas is delivered to the volume selected for the sample loop is based on application
instrument. Excess sample gas may either be returned to the requirements and expected concentrations of siloxane species.
process or vented to atmosphere, dependent on safety concerns The sampling frequency relative to the process bandwidth is
and application requirements. If the sample gas pressure critical to ensuring that the reported analytical results ad-
exceeds 5 psig, it is recommended that a pressure regulator be equately represent the process being monitored. The Nyquist-
installed to reduce the pressure to 5 psig or less. Shannon sampling criterion of a sampling frequency that
exceeds twice the process bandwidth can be used to establish
6.3 Sample Inlet System—The siting and installation of an
3,4
a minimum analytical cycle time. Typical measurement
on-line monitor is critical for collecting representative infor-
frequency is 2-3 times per day, but measurements may be
mation on siloxanes content. Factors that should be considered
acquired up to once per hour.
in siting an instrument include ease of access for repair or
6.3.1 Carrier and Drift Gas Control—Constant flow control
maintenance, sample uniformity at the sampling point, appro-
of carrier and IMS drift gases is critical for optimum and
priateness of samples from a sampling location, ambient
consistent analytical performance. For the specific GC-IMS
conditions, and of course safety issues. All sampling system
analyzer described in this method, ultra-high-purity nitrogen is
componentsincontactwiththefuelstreammustbeconstructed
used for both carrier gas and IMS drift gas. Flow rates and
of inert and organosilicon-free materials. Care should be taken
pressures are maintained by use of electronic pressure control-
to ensure that the extracted sample is maintained as a particu-
lers. Depending on the application and site-specific
late and condensate free gas, which can be accomplished with
requirements, rotameters may be used to control gas flow
the use of an appropriately selected membrane filter. Heat
downstream of the analyzer, whether the gas is being directed
tracing along the sample line to the analyzer is required to
back to the source pipe or is vented to atmosphere. Plumbing
ensure that higher molecular weight siloxane species are kept
should be designed to ensure the pressure of gas within the
in the gas phase. If a membrane filter is included in the
analyzer’s sample loop is as close to one atmosphere pressure
sampling system, or any other components between the sam-
as possible.Temperature control is vital for ensuring consistent
pling connection and the analyzer inlet, they must also be
operationoftheinstrument.Carrier/Driftgaspressuremustnot
heated. It is recommended that all heated components maintain
exceed 6 bar(600 kPa) at the inlet to the analyzer. (See Fig. 2.)
a temperature of at least 65 °C. Sample gas should be brought
to the analyzer continuously and conveyed through a bypass
Nyquist, H., “Certain Topics in Telegraph Transmission Theory,” Trans. AIEE,
loop that either vents to atmosphere or is returned to the source
Vol 47, Apr. 1928, pp. 617-644.
gas pipe. If venting to atmosphere, an appropriately designed
Shannon, C. E., “Communication in the Presence of Noise,” Proc. Institute of
scrubber or control device may be used. Although sample gas Radio Engineers, Vol 37, No. 1, Jan. 1949, pp. 10-21.
D8455 − 22
FIG. 2 GC-IMS Siloxane Analyzer Flow Diagram
6.3.2 Detector—The GC-IMS detector is an electrometer, retention time). The report includes essential information such
which measures a change in electric potential when ionized as device ID, timestamp, and the name of the associated
siloxanes (or any other compounds susceptible to ionization measurement file. The report also includes concentration data
through the tritium-hydronium pathway) pass through the IMS for each individual measured species, as well as the total
drift cell and strike the detector. The magnitude of induced siloxane concentration, the total SiO concentration, and the
electric potential is proportional to the number of ions (and total Si concentration (the latter two are mathematically
therefore concentration of the analyte) striking the detector at derived from the total siloxane concentration, as explained in
any given moment in time. The correlation between ion 11.1).
concentration and change in potential is non-linear, and there- 6.4.1 Data is typically stored locally on the GC-IMS
fore any calibration curve generated will necessarily also be computer,butitmayalsoberetrievedviaUSBconnection.The
non-linear. GC-IMS calibrations for this application typically analyzer may also be configured to au
...