ASTM D2712-23

Standard Test Method for Determination of Hydrocarbon Impurities in High Purity Propylene by Gas Chromatography

SIGNIFICANCE AND USE
5.1 High-purity propylene is required as a feedstock for various manufacturing processes, and the presence of trace amounts of certain hydrocarbon impurities may have adverse effects on yield or catalyst life. This test method is suitable for use as a benchmark in setting commercial specifications, for use as an internal quality control tool, and for use in development or research work.
SCOPE
1.1 This test method is used for the determination of hydrocarbon impurities in propylene (propene) material of 97 % by mass or greater purity (concentrates). These impurities are determined in the concentration range of 0.35 mg/kg to 8575 mg/kg and includes the following components: methane, ethane, ethylene, propane, acetylene, isobutane, propadiene, normal butane, trans-2-butene, butene-1, isobutylene, cis-2-butene, isopentane, methylacetylene, normal pentane, and 1,3-butadiene.
Note 1: Optionally, the analysis may include the determination of pentenes/hexanes and heavier components, see 6.3.  
1.2 This test method does not determine non-hydrocarbon impurities, and additional tests may be necessary to fully characterize the propylene sample. However, for the purposes of this test, the purity of propylene is determined as the difference between the total of the determined analytes and 100 % (by difference).  
1.3 When this test method is being used for the determination of trace level impurities in high-purity propylene, the use of this test method for the analysis of propylene samples at lower purities is not recommended due to the potential for cross contamination between samples.  
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.5 This standard may involve hazardous materials, operations, and equipment. 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.  
1.5.1 The user is advised to obtain LPG safety training for the safe operation of this test method procedure and related activities. The eLearning training course “Liquefied Petroleum Gases Sampling Safety” is available on the ASTM.org website.  
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: 28-Feb-2023
• ICS: 71.080.10 - Aliphatic hydrocarbons
• Technical Committee: D02 - Petroleum Products, Liquid Fuels, and Lubricants
• Drafting Committee: D02.D0 - Hydrocarbons for Chemical and Special Uses

Relations

• Refers: ASTM D1265-23a - Standard Practice for Sampling Liquefied Petroleum (LP) Gases, Manual Method
• Effective Date: 01-Dec-2023
• Refers: ASTM F307-13(2020) - Standard Practice for Sampling Pressurized Gas for Gas Analysis
• Effective Date: 01-Apr-2020
• Refers: ASTM F307-13 - Standard Practice for Sampling Pressurized Gas for Gas Analysis
• Effective Date: 01-Jun-2013
• Refers: ASTM D1835-13 - Standard Specification for Liquefied Petroleum (LP) Gases
• Effective Date: 01-May-2013
• Refers: ASTM D1835-12 - Standard Specification for Liquefied Petroleum (LP) Gases
• Effective Date: 01-Dec-2012
• Refers: ASTM D3700-12 - Standard Practice for Obtaining LPG Samples Using a Floating Piston Cylinder
• Effective Date: 01-Nov-2012
• Refers: ASTM D1835-11 - Standard Specification for Liquefied Petroleum (LP) Gases
• Effective Date: 01-May-2011
• Refers: ASTM F307-02(2007) - Standard Practice for Sampling Pressurized Gas for Gas Analysis
• Effective Date: 01-Apr-2007
• Refers: ASTM E355-96(2007) - Standard Practice for Gas Chromatography Terms and Relationships
• Effective Date: 01-Mar-2007
• Refers: ASTM D3700-07 - Standard Practice for Obtaining LPG Samples Using a Floating Piston Cylinder
• Effective Date: 15-Feb-2007
• Refers: ASTM D1835-05 - Standard Specification for Liquefied Petroleum (LP) Gases
• Effective Date: 01-Apr-2005
• Refers: ASTM D1265-04a - Standard Practice for Sampling Liquefied Petroleum (LP) Gases (Manual Method)
• Effective Date: 01-Nov-2004
• Refers: ASTM D1265-04 - Standard Practice for Sampling Liquefied Petroleum (LP) Gases (Manual Method)
• Effective Date: 01-May-2004
• Refers: ASTM D1835-03a - Standard Specification for Liquefied Petroleum (LP) Gases
• Effective Date: 01-Nov-2003
• Refers: ASTM D1835-03 - Standard Specification for Liquefied Petroleum (LP) Gases
• Effective Date: 10-May-2003

Overview

ASTM D2712-23: Standard Test Method for Determination of Hydrocarbon Impurities in High Purity Propylene by Gas Chromatography is an internationally recognized protocol developed by ASTM. This method is essential for analyzing hydrocarbon impurities in propylene (propene) material with a purity of 97% by mass or greater. The presence of trace hydrocarbon contaminants in high-purity propylene can negatively impact manufacturing yields, catalyst lifespan, and overall product quality. Applying this standard increases the reliability of feedstock materials used in the petrochemical industry, supports quality control, and helps set commercial specifications for propylene.

Key Topics

• Hydrocarbon Impurity Detection: This standard focuses on the precise determination of trace-level hydrocarbon impurities-including methane, ethane, ethylene, propane, acetylene, isobutane, butenes, isopentane, methylacetylene, pentanes, and 1,3-butadiene-within a quantification range of 0.35 mg/kg to 8575 mg/kg.

• Gas Chromatography (GC) Technique: The analysis employs gas chromatography equipped preferably with a flame ionization detector (FID) for high sensitivity and selectivity. Specialized sample introduction systems, such as liquid or vapor sampling valves and the use of pre-columns, help ensure effective separation and accurate quantification.

• Sample Preparation and Calibration: Guidelines are provided for proper sample collection (using floating piston sample cylinders to prevent volatilization and headspace formation) and for calibration using certified external standard mixtures. The purity of propylene is measured by subtracting the total impurities detected from 100% by mass.

• Quality Assurance: The methodology supports routine benchmarking, process control, and R&D in order to maintain the performance expectations of high-purity propylene across industrial applications.

• Safety Considerations: The procedure handles hazardous materials under pressure and requires robust safety, health, and environmental practices. Personnel should receive LPG sampling safety training and observe all applicable regulatory requirements.

Applications

• Feedstock Qualification: Used by propylene producers and processors to certify high-purity feedstocks for sensitive polymerization reactions and production of chemical intermediates.
• Commercial Specification Setting: Provides a technical basis for defining and verifying impurity limits in supply contracts, securing confidence in material quality for both buyers and sellers.
• Quality Control and Assurance: Integrates into plant laboratory workflows for continuous monitoring of product streams, helping to quickly identify off-spec batches and minimize process disruptions.
• Process Development and Research: Utilized in research laboratories and pilot plants to evaluate the effect of trace impurities on catalyst activity, polymer properties, and overall process efficiency.

Related Standards

• ASTM D1265: Practice for Sampling Liquefied Petroleum (LP) Gases, Manual Method - Guidance for correct sampling techniques supporting D2712-23.
• ASTM D1835: Specification for Liquefied Petroleum (LP) Gases - Specifies composition and impurity levels for commercial LPG products.
• ASTM D3700: Practice for Obtaining LPG Samples Using a Floating Piston Cylinder - Describes recommended sampling containers referenced in D2712-23.
• ASTM E355: Practice for Gas Chromatography Terms and Relationships - Provides definitions and terminology pertinent to GC analysis.
• ASTM F307: Practice for Sampling Pressurized Gas for Gas Analysis - Alternative procedures for safe and effective gas sample collection.

By following ASTM D2712-23, industries ensure accurate detection of hydrocarbon impurities, supporting stringent quality standards for propylene feedstocks. Its adoption drives process optimization and regulatory compliance across the petrochemical sector.

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: D2712 − 23
Standard Test Method for
Determination of Hydrocarbon Impurities in High Purity
Propylene by Gas Chromatography
This standard is issued under the fixed designation D2712; 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* activities. The eLearning training course “Liquefied Petroleum
Gases Sampling Safety” is available on the ASTM.org website.
1.1 This test method is used for the determination of
1.6 This international standard was developed in accor-
hydrocarbon impurities in propylene (propene) material of
dance with internationally recognized principles on standard-
97 % by mass or greater purity (concentrates). These impurities
ization established in the Decision on Principles for the
are determined in the concentration range of 0.35 mg ⁄kg to
Development of International Standards, Guides and Recom-
8575 mg/kg and includes the following components: methane,
mendations issued by the World Trade Organization Technical
ethane, ethylene, propane, acetylene, isobutane, propadiene,
Barriers to Trade (TBT) Committee.
normal butane, trans-2-butene, butene-1, isobutylene, cis-2-
butene, isopentane, methylacetylene, normal pentane, and
2. Referenced Documents
1,3-butadiene.
2.1 ASTM Standards:
NOTE 1—Optionally, the analysis may include the determination of
D1265 Practice for Sampling Liquefied Petroleum (LP)
pentenes/hexanes and heavier components, see 6.3.
Gases, Manual Method
1.2 This test method does not determine non-hydrocarbon
D1835 Specification for Liquefied Petroleum (LP) Gases
impurities, and additional tests may be necessary to fully
D3700 Practice for Obtaining LPG Samples Using a Float-
characterize the propylene sample. However, for the purposes
ing Piston Cylinder
of this test, the purity of propylene is determined as the
E355 Practice for Gas Chromatography Terms and Relation-
difference between the total of the determined analytes and
ships
100 % (by difference).
F307 Practice for Sampling Pressurized Gas for Gas Analy-
1.3 When this test method is being used for the determina-
sis
tion of trace level impurities in high-purity propylene, the use
of this test method for the analysis of propylene samples at 3. Terminology
lower purities is not recommended due to the potential for
3.1 Definitions:
cross contamination between samples.
3.1.1 Additional terminology related to the practice of gas
1.4 The values stated in SI units are to be regarded as chromatography can be found in Practice E355.
standard. No other units of measurement are included in this 3.1.2 liquefied petroleum gas (LPG), n—hydrocarbon gases
standard. that can be stored or handled in the liquid phase through
compression or refrigeration, or both.
1.5 This standard may involve hazardous materials,
3.1.2.1 Discussion—LPG’s generally consist of C and C
3 4
operations, and equipment. This standard does not purport to
alkanes and alkenes or mixtures thereof and containing less
address all of the safety concerns, if any, associated with its
than 10 % by volume of higher carbon number material. Vapor
use. It is the responsibility of the user of this standard to
pressure does not normally exceed 2000 kPa at 40 ºC.
establish appropriate safety, health, and environmental prac-
tices and determine the applicability of regulatory limitations 3.2 Definitions of Terms Specific to This Standard:
prior to use. 3.2.1 propane/propene mixtures, n—mixtures primarily
1.5.1 The user is advised to obtain LPG safety training for composed of propane and propene where one of these compo-
the safe operation of this test method procedure and related nents is usually in the concentration range of 30 % to 85 % by
mass with the other comprising the majority of the remainder.
This test method is under the jurisdiction of ASTM Committee D02 on
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
Subcommittee D02.D0 on Hydrocarbons for Chemical and Special Uses. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved March 1, 2023. Published March 2023. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 1968. Last previous edition approved in 2020 as D2712 – 20. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/D2712-23. the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D2712 − 23
Commercial Propane in Specification D1835 is typically this 6.3 Column(s)—The recommended analytical column is a
sort of product mixture. 50 m by 0.53 mm I.D. KCl deactivated Al O PLOT column.
2 3
3.2.1.1 Discussion—Other components may be present, Relative retention order is dependent upon the deactivation
usually at less than 10 % by mass. method of the column. Users are cautioned to specifically test
the column using a test mix to ensure that propadiene, methyl
4. Summary of Test Method
acetylene, and butadiene are not being adsorbed by the column.
4.1 An LPG phase sample is analyzed as received via either This condition can exist depending upon the degree of column
gas or liquid sampling valves into a gas chromatograph. The deactivation. Other types of columns may be used so long as
gas chromatograph is provided with a liquid sampling valve they provide sufficient separation and no absorption of
and optionally with a 6-port gas sampling valve and/or a 6-port
propadiene, methyl acetylene, or butadiene occurs.
switching valve. If the user chooses to use a 6-port switching
6.4 Inlet—The gas chromatograph must include a splitter
valve to provide an initial composite backflush of C olefins
inlet, which may be operated isothermally at user-settable
and C + components, a small length of pre-column should be
temperatures up to the maximum column temperature em-
used to provide separation of the components of interest, as
ployed. Split flows in the range of 5:1 to 8:1 might be
listed in 1.1, and the heavier components. This pre-column will
employed; a typical value for the split ratio is 5:1 using a
separate the heaviest components from the remainder of the
0.2 μL liquid sampling valve injection (to allow the lower
sample. A pre-column which also retains water and oxygenated
detection limits described to be obtained). The splitter inlet is
hydrocarbons is recommended. A flame ionization detector
used in conjunction with gas or liquid sampling valves, as
(FID) is used for component detection. However, other detec-
described below.
tors may be used provided that they can provide the same
6.4.1 The user may wish to incorporate the use of a 6-port
sensitivity and selectivity for the components of interest.
switching valve and pre-column(s) to provide an initial C
4.2 The integrated detector signal (peak areas) is corrected
olefin/C + composite backflush. Any pre-columns which pro-
for detector response by comparing sample peak areas for each
vide separation between the components of interest and the
compound of interest relative to peak areas obtained for each
composite heavier components may be used. A 10 m to 15 m
compound of interest from a standard mixture of known
section of 0.53 mm I.D. by 3 micro polydimethylpolysiloxane
component concentrations. This method of calibration shall be
is recommended. The length of a pre-column will be dependent
referred to hereafter as “external standard calibration.”
upon the film thickness, phase, and/or column activity. This
pre-column separates the heaviest components away from the
5. Significance and Use
remainder of the sample.
5.1 High-purity propylene is required as a feedstock for
various manufacturing processes, and the presence of trace 6.5 Sample Introduction:
amounts of certain hydrocarbon impurities may have adverse
6.5.1 Liquid Sampling—Liquid samples shall be injected by
effects on yield or catalyst life. This test method is suitable for
means of a liquid sampling valve with an internal fixed sample
use as a benchmark in setting commercial specifications, for
loop which will provide the minimum detection limits as
use as an internal quality control tool, and for use in develop-
specified in 1.1. A sample loop size of 0.2 μL has been found
ment or research work.
to be sufficient. The liquid sample being introduced must be
pressurized at least 1380 kPa above the vapor pressure of the
6. Apparatus
sample at the valve temperature at all times (use of a constant
6.1 Gas Chromatograph (GC)—Any gas chromatographic
pressure source is suggested, if possible). It is important that
instrument that is capable of providing a linear temperature
this pressure be duplicated to ensure repeatability. A shut-off
programmed zone for the capillary column(s). The program-
valve or back-pressure regulator should be located at the waste
ming rate must be sufficiently repeatable to obtain a retention
exit of the liquid sampling valve so that sample pressure to the
time repeatability of 0.05 min (3 s) throughout the scope of this
valve may be maintained.
analysis.
6.5.1.1 Figs. 1 and 2—A frit type filter should be placed in
6.2 Detector—Any detector providing a sensitivity of the sample line in front of the liquid sampling valve so that
0.5 mg ⁄kg or less for the compounds listed in 1.1 may be used. particulates that might be present in samples will not score the
The use of a flame ionization detector (FID) is strongly valve rotor. A frit size of 2 μm to 7 μm is suggested. It is very
recommended. However, other detectors may be used provided important that the filter has a low-pressure drop. A high-
that they can provide the same sensitivity and selectivity for the pressure drop across a filter will cause the sample to boil across
components of interest without interference from the propylene the filter, causing non-repeatable results. The liquid sample
major peak or non-hydrocarbon components, which might be valve shall be mounted exterior to any heated compartment and
present in the samples. As an example, the use of a mass shall be able to operate at ambient temperature. The use of
spectroscopic detector (MSD), a discharge ionization detector floating piston sample cylinders is encouraged to minimize or
(DID), or helium ionization detector (HID) might be possible eliminate the volatilization of lighter components into the
so long as appropriate valving is supplied and/or appropriate headspace. The fixed sample volume injection should be
testing is performed to ensure that non-hydrocarbon compo- repeatable such that successive runs agree within 2 % relative
nents will not interfere. All calculations in this test method are on each component area and all components are within the
based on the use of a flame ionization detector (FID). linearity of the detector. (2 % relative on each component is not
D2712 − 23
FIG. 1 Arrangement of Valves
FIG. 2 Arrangement of Valves
achieved in the precision data set of this test method for typical arrangement of the valves is shown in Fig. 1 and Fig. 2,
ethylene > 5 % and acetylene >3.5 %) or in Fig. 3 and Fig. 4 if the gas sampling valve is used. To
6.5.2 Vapor Sampling (optio
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D2712 − 20 D2712 − 23
Standard Test Method for
Determination of Hydrocarbon Impurities in High Purity
Propylene by Gas Chromatography
This standard is issued under the fixed designation D2712; 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*
1.1 This test method is used for the determination of hydrocarbon impurities in propylene (propene) material of 97 % by mass or
greater purity (concentrates). These impurities are determined in the concentration range of 0.35 mg ⁄kg to 8575 mg/kg and
includes the following components: methane, ethane, ethylene, propane, acetylene, isobutane, propadiene, normal butane,
trans-2-butene, butene-1, isobutylene, cis-2-butene, isopentane, methylacetylene, normal pentane, and 1,3-butadiene.
NOTE 1—Optionally, the analysis may include the determination of pentenes/hexanes and heavier components, see 6.3.
1.2 This test method does not determine non-hydrocarbon impurities, and additional tests may be necessary to fully characterize
the propylene sample. However, for the purposes of this test, the purity of propylene is determined as the difference between the
total of the determined analytes and 100 % (by difference).
1.3 When this test method is being used for the determination of trace level impurities in high-purity propylene, the use of this
test method for the analysis of propylene samples at lower purities is not recommended due to the potential for cross contamination
between samples.
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.5 This standard may involve hazardous materials, operations, and equipment. 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.
1.5 This standard may involve hazardous materials, operations, and equipment. 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.
1.5.1 The user is advised to obtain LPG safety training for the safe operation of this test method procedure and related activities.
The eLearning training course “Liquefied Petroleum Gases Sampling Safety” is available on the ASTM.org website.
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.
This test method is under the jurisdiction of ASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcommittee
D02.D0 on Hydrocarbons for Chemical and Special Uses.
Current edition approved July 1, 2020March 1, 2023. Published July 2020March 2023. Originally approved in 1968. Last previous edition approved in 20182020 as D2712
– 18a. DOI: 10.1520/D2712-20.20. DOI: 10.1520/D2712-23.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D2712 − 23
2. Referenced Documents
2.1 ASTM Standards:
D1265 Practice for Sampling Liquefied Petroleum (LP) Gases, Manual Method
D1835 Specification for Liquefied Petroleum (LP) Gases
D3700 Practice for Obtaining LPG Samples Using a Floating Piston Cylinder
E355 Practice for Gas Chromatography Terms and Relationships
F307 Practice for Sampling Pressurized Gas for Gas Analysis
3. Terminology
3.1 Definitions:
3.1.1 Additional terminology related to the practice of gas chromatography can be found in Practice E355.
3.1.2 liquefied petroleum gas (LPG), n—hydrocarbon gases that can be stored or handled in the liquid phase through compression
or refrigeration, or both.
3.1.2.1 Discussion—
LPG’s generally consist of C and C alkanes and alkenes or mixtures thereof and containing less than 10 % by volume of higher
3 4
carbon number material. Vapor pressure does not normally exceed 2000 kPa at 40 ºC.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 propane/propene mixtures, n—mixtures primarily composed of propane and propene where one of these components is
usually in the concentration range of 30 % to 85 % by mass with the other comprising the majority of the remainder. Commercial
Propane in Specification D1835 is typically this sort of product mixture.
3.2.1.1 Discussion—
Other components may be present, usually at less than 10 % by mass.
4. Summary of Test Method
4.1 An LPG phase sample is analyzed as received via either gas or liquid sampling valves into a gas chromatograph. The gas
chromatograph is provided with a liquid sampling valve and optionally with a 6-port gas sampling valve and/or a 6-port switching
valve. If the user chooses to use a 6-port switching valve to provide an initial composite backflush of C olefins and C +
5 6
components, a small length of pre-column should be used to provide separation of the components of interest, as listed in 1.1, and
the heavier components. This pre-column will separate the heaviest components from the remainder of the sample. A pre-column
which also retains water and oxygenated hydrocarbons is recommended. A flame ionization detector (FID) is used for component
detection. However, other detectors may be used provided that they can provide the same sensitivity and selectivity for the
components of interest.
4.2 The integrated detector signal (peak areas) is corrected for detector response by comparing sample peak areas for each
compound of interest relative to peak areas obtained for each compound of interest from a standard mixture of known component
concentrations. This method of calibration shall be referred to hereafter as “external standard calibration.”
5. Significance and Use
5.1 High-purity propylene is required as a feedstock for various manufacturing processes, and the presence of trace amounts of
certain hydrocarbon impurities may have adverse effects on yield or catalyst life. This test method is suitable for use as a
benchmark in setting commercial specifications, for use as an internal quality control tool, and for use in development or research
work.
6. Apparatus
6.1 Gas Chromatograph (GC)—Any gas chromatographic instrument that is capable of providing a linear temperature
programmed zone for the capillary column(s). The programming rate must be sufficiently repeatable to obtain a retention time
repeatability of 0.05 min (3 s) throughout the scope of this analysis.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
D2712 − 23
6.2 Detector—Any detector providing a sensitivity of 0.5 mg ⁄kg or less for the compounds listed in 1.1 may be used. The use of
a flame ionization detector (FID) is strongly recommended. However, other detectors may be used provided that they can provide
the same sensitivity and selectivity for the components of interest without interference from the propylene major peak or
non-hydrocarbon components, which might be present in the samples. As an example, the use of a mass spectroscopic detector
(MSD), a discharge ionization detector (DID), or helium ionization detector (HID) might be possible so long as appropriate valving
is supplied and/or appropriate testing is performed to ensure that non-hydrocarbon components will not interfere. All calculations
in this test method are based on the use of a flame ionization detector (FID).
6.3 Column(s)—The recommended analytical column is a 50 m by 0.53 mm I.D. KCl deactivated Al O PLOT column. Relative
2 3
retention order is dependent upon the deactivation method of the column. Users are cautioned to specifically test the column using
a test mix to ensure that propadiene, methyl acetylene, and butadiene are not being adsorbed by the column. This condition can
exist depending upon the degree of column deactivation. Other types of columns may be used so long as they provide sufficient
separation and no absorption of propadiene, methyl acetylene, or butadiene occurs.
6.4 Inlet—The gas chromatograph must include a splitter inlet, which may be operated isothermally at user-settable temperatures
up to the maximum column temperature employed. Split flows in the range of 5:1 to 8:1 might be employed; a typical value for
the split ratio is 5:1 using a 0.2 μL liquid sampling valve injection (to allow the lower detection limits described to be obtained).
The splitter inlet is used in conjunction with gas or liquid sampling valves, as described below.
6.4.1 The user may wish to incorporate the use of a 6-port switching valve and pre-column(s) to provide an initial C olefin/C +
5 6
composite backflush. Any pre-columns which provide separation between the components of interest and the composite heavier
components may be used. A 10 m to 15 m section of 0.53 mm I.D. by 3 micro polydimethylpolysiloxane is recommended. The
length of a pre-column will be dependent upon the film thickness, phase, and/or column activity. This pre-column separates the
heaviest components away from the remainder of the sample.
6.5 Sample Introduction:
6.5.1 Liquid Sampling—Liquid samples shall be injected by means of a liquid sampling valve with an internal fixed sample loop
which will provide the minimum detection limits as specified in 1.1. A sample loop size of 0.2 μL has been found to be sufficient.
The liquid sample being introduced must be pressurized at least 1380 kPa above the vapor pressure of the sample at the valve
temperature at all times (use of a constant pressure source is suggested, if possible). It is important that this pressure be duplicated
to ensure repeatability. A shut-off valve or back-pressure regulator should be located at the waste exit of the liquid sampling valve
so that sample pressure to the valve may be maintained.
6.5.1.1 Figs. 1 and 2—A frit type filter should be placed in the sample line in front of the liquid sampling valve so that particulates
that might be present in samples will not score the valve rotor. A frit size of 2 μm to 7 μm is suggested. It is very important that
the filter has a low-pressure drop. A high-pressure drop across a filter will cause the sample to boil across the filter, causing
non-repeatable results. The liquid sample valve shall be mounted exterior to any heated compartment and shall be able to operate
FIG. 1 Arrangement of Valves
D2712 − 23
FIG. 2 Arrangement of Valves
at ambient temperature. The use of floating piston sample cylinders is encouraged to minimize or eliminate the volatilization of
lighter components into the headspace. The fixed sample volume injection should be repeatable such that successive runs agree
within 2 % relative on each component area and all components are within the linearity of the detector. (2 % relative on each
component i
...