ASTM D2163-23e1

Standard Test Method for Determination of Hydrocarbons in Liquefied Petroleum (LP) Gases and Propane/Propene Mixtures by Gas Chromatography

SIGNIFICANCE AND USE
5.1 The hydrocarbon component distribution of liquefied petroleum gases and propene mixtures is often required for end-use sale of this material. Applications such as chemical feed stocks or fuel require precise compositional data to ensure uniform quality. Trace amounts of some hydrocarbon impurities in these materials can have adverse effects on their use and processing.  
5.2 The component distribution data of liquefied petroleum gases and propene mixtures can be used to calculate physical properties such as relative density, vapor pressure, and motor octane (see Practice D2598). Precision and accuracy of compositional data are extremely important when these data are used to calculate various properties of these petroleum products.
SCOPE
1.1 This test method covers the quantitative determination of individual hydrocarbons in liquefied petroleum (LP) gases and mixtures of propane and propene, excluding high-purity propene in the range of C1 to C5. Component concentrations are determined in the range of 0.01 % to 100 % by volume.  
1.2 This test method does not fully determine hydrocarbons heavier than C5 and non-hydrocarbon materials, and additional tests may be necessary to fully characterize an LPG sample.  
1.3 The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only.  
1.4 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.  
1.4.1 The user is advised to obtain LPG safety training for the safe operation of this test method procedure and related activities.  
1.5 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: 75.160.30 - Gaseous fuels
• Technical Committee: D02 - Petroleum Products, Liquid Fuels, and Lubricants
• Drafting Committee: D02.D0.03 - Propylene

Relations

• Refers: ASTM D1265-23a - Standard Practice for Sampling Liquefied Petroleum (LP) Gases, Manual Method
• Effective Date: 01-Dec-2023
• Refers: ASTM E594-96(2019) - Standard Practice for Testing Flame Ionization Detectors Used in Gas or Supercritical Fluid Chromatography
• Effective Date: 01-Sep-2019
• 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 E594-96(2011) - Standard Practice for Testing Flame Ionization Detectors Used in Gas or Supercritical Fluid Chromatography
• Effective Date: 01-Nov-2011
• Refers: ASTM D1835-11 - Standard Specification for Liquefied Petroleum (LP) Gases
• Effective Date: 01-May-2011
• Refers: ASTM D6729-04(2009) - Standard Test Method for Determination of Individual Components in Spark Ignition Engine Fuels by 100 Metre Capillary High Resolution Gas Chromatography
• Effective Date: 15-Apr-2009
• Refers: ASTM D2598-02(2007) - Standard Practice for Calculation of Certain Physical Properties of Liquefied Petroleum (LP) Gases from Compositional Analysis
• Effective Date: 01-Jul-2007
• Refers: ASTM D2421-02(2007) - Standard Practice for Interconversion of Analysis of C<i><inf>5</inf></i> and Lighter Hydrocarbons to Gas-Volume, Liquid-Volume, or Mass Basis
• Effective Date: 01-May-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 E594-96(2006) - Standard Practice for Testing Flame Ionization Detectors Used in Gas or Supercritical Fluid Chromatography
• Effective Date: 01-Mar-2006
• Refers: ASTM D1835-05 - Standard Specification for Liquefied Petroleum (LP) Gases
• Effective Date: 01-Apr-2005
• Refers: ASTM E1510-95(2005) - Standard Practice for Installing Fused Silica Open Tubular Capillary Columns in Gas Chromatographs
• Effective Date: 01-Feb-2005

Overview

ASTM D2163-23e1 – Standard Test Method for Determination of Hydrocarbons in Liquefied Petroleum (LP) Gases and Propane/Propene Mixtures by Gas Chromatography is a key international standard published by ASTM. This standard defines a precise method for the quantitative determination of individual hydrocarbons in liquefied petroleum gases (LPG) and mixtures of propane and propene (excluding high-purity propene) using gas chromatography. Accurate hydrocarbon composition analysis is essential for the certification and quality assurance of fuels and chemical feedstocks, helping stakeholders meet regulatory and market requirements.

Key Topics

• Scope of Measurement

  • Measures C1 to C5 hydrocarbons in LP gases and propane/propene mixtures.
  • Determines component concentrations in a wide range (0.01% to 100% by volume).
  • Does not fully identify hydrocarbons heavier than C5 or non-hydrocarbon materials.

• Methodology

  • Utilizes gas chromatography, typically with a flame ionization detector (FID).
  • Sample introduction can be done by liquid or vapor phase methods.
  • Calibration relies on certified reference standards.

• Significance

  • Ensures product quality for commercial sale, fuel applications, and use as chemical feedstocks.
  • Enables calculation of important physical properties (e.g., vapor pressure, relative density, motor octane).
  • Assists in identifying trace impurities that could impact performance or safety.

• Safety and Compliance

  • Users are responsible for following safety, health, and environmental guidelines.
  • LPG safety training is recommended for those handling samples and equipment.

Applications

• Fuel Quality Control

  • Used by laboratories and refineries to confirm the composition of LPG, propane, and propane/propene mixtures for fuel distribution.
  • Detection and quantification of hydrocarbon content help ensure compliance with fuel standards.

• Chemical Feedstocks

  • Provides essential data for industries using LPG products as raw materials for chemical synthesis.
  • Precise component analysis guarantees material specifications and processing efficiency.

• Regulatory Compliance

  • Supports accurate reporting and documentation in line with national and international fuel and environmental regulations.
  • Facilitates trade by providing consistent, standardized analytical results across the global supply chain.

• Physical Property Calculations

  • The compositional data obtained are used to calculate key properties such as vapor pressure and octane rating, which are critical for product certification and application suitability.

Related Standards

The ASTM D2163-23e1 standard references and complements several other standards and practices relevant to the analysis and handling of LPG products, including:

• ASTM D1265 – Practice for Sampling Liquefied Petroleum (LP) Gases (Manual Method)
• ASTM D1835 – Specification for Liquefied Petroleum (LP) Gases
• ASTM D2421 – Practice for Interconversion of Analysis of C5 and Lighter Hydrocarbons
• ASTM D2598 – Practice for Calculation of Physical Properties of LPG from Compositional Analysis
• ASTM D3700 – Practice for Obtaining LPG Samples Using a Floating Piston Cylinder
• ASTM D6729 – Test Method for Determination of Components in Spark Ignition Engine Fuels by High-Resolution Gas Chromatography
• ASTM E355 – Practice for Gas Chromatography Terms and Relationships

Practical Value

Adopting ASTM D2163-23e1 ensures laboratories, refineries, and distributors can produce accurate, reliable hydrocarbon composition data for LPG and related products. This supports quality assurance, regulatory compliance, and safe usage in the fuel and chemical industries. By employing this standardized gas chromatography method, organizations can maintain uniform testing protocols, enabling efficient product specification, troubleshooting, and trade across international markets.

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.
´1
Designation: D2163 − 23
Standard Test Method for
Determination of Hydrocarbons in Liquefied Petroleum (LP)
Gases and Propane/Propene Mixtures by Gas
Chromatography
This standard is issued under the fixed designation D2163; 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.
ε NOTE—Editorially updated scope in April 2023.
1. Scope* 2. Referenced Documents
2.1 ASTM Standards:
1.1 This test method covers the quantitative determination
D1265 Practice for Sampling Liquefied Petroleum (LP)
of individual hydrocarbons in liquefied petroleum (LP) gases
Gases, Manual Method
and mixtures of propane and propene, excluding high-purity
D1835 Specification for Liquefied Petroleum (LP) Gases
propene in the range of C to C . Component concentrations
1 5
D2421 Practice for Interconversion of Analysis of C and
are determined in the range of 0.01 % to 100 % by volume.
Lighter Hydrocarbons to Gas-Volume, Liquid-Volume, or
1.2 This test method does not fully determine hydrocarbons
Mass Basis
heavier than C and non-hydrocarbon materials, and additional
5 D2598 Practice for Calculation of Certain Physical Proper-
tests may be necessary to fully characterize an LPG sample.
ties of Liquefied Petroleum (LP) Gases from Composi-
tional Analysis
1.3 The values stated in SI units are to be regarded as
D3700 Practice for Obtaining LPG Samples Using a Float-
standard. The values given in parentheses are for information
ing Piston Cylinder
only.
D6729 Test Method for Determination of Individual Com-
1.4 This standard does not purport to address all of the ponents in Spark Ignition Engine Fuels by 100 Metre
Capillary High Resolution Gas Chromatography
safety concerns, if any, associated with its use. It is the
E355 Practice for Gas Chromatography Terms and Relation-
responsibility of the user of this standard to establish appro-
ships
priate safety, health, and environmental practices and deter-
E594 Practice for Testing Flame Ionization Detectors Used
mine the applicability of regulatory limitations prior to use.
in Gas or Supercritical Fluid Chromatography
1.4.1 The user is advised to obtain LPG safety training for
E1510 Practice for Installing Fused Silica Open Tubular
the safe operation of this test method procedure and related
Capillary Columns in Gas Chromatographs
activities.
2.2 Canadian General Standards Board Publications:
1.5 This international standard was developed in accor-
CAN/CGSB 3.0 No. 14.3 Standard Test Method for the
dance with internationally recognized principles on standard-
Identification of Hydrocarbon Components in Automotive
ization established in the Decision on Principles for the
Gasoline Using Gas Chromatography
Development of International Standards, Guides and Recom-
2.3 Gas Processors Association:
mendations issued by the World Trade Organization Technical
GPA Std 2145-03 for Hexane
Barriers to Trade (TBT) Committee.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
This test method is under the jurisdiction of ASTM Committee D02 on Standards volume information, refer to the standard’s Document Summary page on
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of the ASTM website.
Subcommittee D02.D0.03 on Propylene. Available from CGSB, Canadian General Standards Board, Gatineau, Canada
Current edition approved March 1, 2023. Published March 2023. Originally K1A 1G6. Visit the CGSB website, www.pwgsc.gc.ca/cgsb/
approved in 1963. Last previous edition approved in 2019 as D2163 – 14 (2019). Available from Gas Processors Association (GPA), 6526 E. 60th St., Tulsa, OK
DOI: 10.1520/D2163-23E01. 74145, http://www.gasprocessors.com.
*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
´1
D2163 − 23
3. Terminology end-use sale of this material. Applications such as chemical
feed stocks or fuel require precise compositional data to ensure
3.1 Definitions:
uniform quality. Trace amounts of some hydrocarbon impuri-
3.1.1 Additional terminology related to the practice of gas
ties in these materials can have adverse effects on their use and
chromatography can be found in Practice E355.
processing.
3.1.2 liquefied petroleum gas (LPG), n—hydrocarbon gases
that can be stored or handled in the liquid phase through 5.2 The component distribution data of liquefied petroleum
compression or refrigeration, or both. gases and propene mixtures can be used to calculate physical
3.1.2.1 Discussion—LPGs generally consist of C and C properties such as relative density, vapor pressure, and motor
3 4
alkanes and alkenes or mixtures thereof and containing less octane (see Practice D2598). Precision and accuracy of com-
than 10 % by volume of higher carbon number material. Vapor positional data are extremely important when these data are
pressure does not normally exceed 2000 kPa at 40 °C. used to calculate various properties of these petroleum prod-
ucts.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 propane/propene mixtures, n—mixtures primarily
6. Apparatus
composed of propane and propene where one of these compo-
nents is usually in the concentration range of 30 % to 85 % by 6.1 Gas Chromatograph (GC)—Any gas chromatographic
mass with the other comprising the majority of the remainder.
instrument provided with a linear temperature programmable
“Commercial Propane” in Specification D1835 is typically this column oven. The temperature control must be capable of
sort of product mixture.
obtaining a retention time repeatability of 0.05 min (3 s)
3.2.1.1 Discussion—Other components may be present, throughout the scope of this analysis.
usually at less than 10 % by mass.
6.2 Detector—A flame ionization detector (FID) having a
sensitivity of 0.5 ppm (mole) or less for the compounds listed
4. Summary of Test Method
in Table 1 is strongly recommended (see Practice E594).
4.1 An LPG sample is analyzed via either liquid or gas
6.2.1 Other detectors may be used (alone or in series)
sampling valves by gas chromatography and compared to
provided that they have sufficient response, linearity, and
corresponding components separated under identical operating
sensitivity to measure the components of interest at the
conditions from a reference standard mixture of known com-
concentration levels required.
position or from use of pure hydrocarbons. The chromatogram
6.3 Data Acquisition—Any commercial integrator or com-
of the sample is interpreted by comparing peak retention times
puterized data acquisition system may be used for display of
and areas with those obtained for the reference standard
the chromatographic detector signal and peak area integration.
mixture or pure hydrocarbons.
The device should be capable of calibration and reporting of
5. Significance and Use the final response corrected results.
5.1 The hydrocarbon component distribution of liquefied 6.4 Sample Introduction—Whether liquid or vapor
petroleum gases and propene mixtures is often required for sampling, the combination of valve injection size and split ratio
TABLE 1 Expected Retention Order and Times
Estimated Retention Time (min) Estimated Retention Time (min)
Component (using typical Al O (using typical 100 m Dimethylpolysiloxane FID TCD
2 3
PLOT operating conditions) column operating conditions)
+ A
C Olefin/C Composite (back-flush) NA . x x
5 6
A
Air Composite (O , Ar, N , Co) NA . . x
2 2
Methane 1.9 6.5 x x
Ethane 2.1 6.7 x x
Propane 2.7 7.3 x x
Cyclopropane 3.4 . x x
Propene 3.5 7.2 x x
2-Methyl Propane (Isobutane) 4.0 8.4 x x
Butane 4.2 9.5 x x
Propadiene 4.7 . x x
Ethyne (Acetylene) 5.0 . x x
Trans-2-Butene 5.5 9.9 x x
1-Butene 5.6 9.2 x x
2-Methyl Propene (Isobutene) 5.7 9.1 x x
2,2-Dimethylpropane (Neopentane) 5.9 10.1 x x
Cis-2-Butene 6.2 10.6 x x
Cyclopentane 6.7 25.8 x x
2-Methyl Butane (Isopentane) 6.8 14.0 x x
Pentane 7.2 16.9 x x
1,3-Butadiene 7.5 9.3 x x
Propyne (Methyl Acetylene) 7.9 . x x
B
>nC (Sum C Olefins and Heavier) 8.1 until end of run . x x
5 5
A
Not applicable.
B
>nC components may be speciated and reported individually.
´1
D2163 − 23
must be selected such that the required sensitivity is achieved olefin/C + determination for this analysis. The back-flush
and also that no component concentration in a sample is greater configuration should be configured according to the manufac-
than the detector upper linearity limit. turer’s recommendations.
6.4.1 If capillary columns will be used, then the GC must
6.7 Columns—Condition all columns used according to the
include a heated, splitting-type injector that is operated isother-
manufacturers’ suggestions prior to use.
mally. Split ratios in the range of 5:1 to 200:1, with a typical
6.7.1 Analytical Column—The recommended analytical col-
value of 100:1, will be used dependent upon the sample
umn is a 50 m by 0.53 mm (ID) Na SO deactivated Al O
2 4 2 3
injection volume and sensitivity required. If packed columns
porous layer open tubular (PLOT) column. Relative retention
will be used, then a splitting-type injector is not required and a
order is dependent upon the deactivation method for the
suitable packed inlet port may be used.
column. (Warning—Specifically test the column to ensure that
6.4.2 Liquid Sampling (recommended)—The GC should be
the column does not adsorb propadiene and butadienes. This
equipped with a liquid sampling valve for introduction of the
condition can exist depending upon the degree of column
sample aliquot to the splitting injector. Liquid sampling valves
deactivation.)
with an internal fixed sample volume between 0.2 μL to 0.5 μL
6.7.1.1 Routine re-conditioning of the column may be
or a size to provide the minimum detection limits given in 1.1
required to maintain column performance.
have been used satisfactorily. The valve shall be rated for at
6.7.1.2 Alternatively, any column(s) that provides the ap-
least 1380 kPa (200 psi) above the vapor pressure of the sample
propriate component separations may be used. Columns
at the valve operating temperature. A shut-off valve shall be
(100 m by 0.25 mm (ID) by 0.5 μm film thickness) employed
provided at the exit of the sampling valve waste port. A 2 μm
in standard methods Test Method D6729 and CGSB 3.0 No.
to 7 μm packed-screen type filter should be provided at the
14.3 have been successfully used.
sample inlet port of the sampling valve to remove possible
6.7.2 Pre-Column (optional)—If an initial back-flush of the
particulate material from the sample. The valve shall provide
C olefins or hexane plus (C +) components, or both, through
5 6
for a repeatability of at least 2 % relative sample volume
the use of the sequence reversal/back-flush valve is desired, a
introduction. The sampling valve shall be located at the GC
second column is required. Any pre-column that provides
such that it can be operated at ambient temperature. The use of
separation between the components of interest and the com-
floating piston sample cylinders is encouraged to minimize or
posite heavier components may be used. Choices may include
eliminate the volatilization of lighter components into the
lengths of column such as a 10 m to 30 m section of 0.53 mm
headspace. Common 80 % filled LPG storage cylinders should
(ID) 1 μm film thickness dimethylpolysiloxane or polyethylene
be pressurized with an inert gas such as helium to facilitate
glycol capillary column or a 9 cm to 15 cm section of the same
liquid transfer and accurate liquid injections. A minimum
column material as the analytical column or any pre-column
pressure of 200 psi above sample vapor pressure is recom-
that provides the desired retention of C olefins, hexanes, and
mended. A pressure gauge may be used to make this determi-
heavier components. This pre-column acts to keep the heavier
nation. Before pressurization, verify that the sample cylinder,
components away from the analytical column and to back-flush
transfer lines and valves are rated to safely contain the
the heavier components as a composite peak to the detector for
pressurized sample. It is customary to add a check valve
quantitation. A pre-column that also has the ability to retain
between the helium cylinder and the sample cylinder to prevent
water and oxygenated hydrocarbon compounds is recom-
contamination in the event the sample cylinder is higher in
mended to keep those materials from entering the analytical
pressure than the pressurizing cylinder.
column.
6.4.3 Vapor Sampling (optional)—A six-port gas sampling
valve or a ten-port sampling/column switching valve with
7. Reagents and Materials
1.6 mm ( ⁄16 in.) fittings and a 200 μL fixed sampling loop may
be provided. This valve shall be contained in a heated
7.1 Carrier Gases—For carrier gases, it is recommended to
enclosure and operated at a temperature above the boiling point
install commercial active oxygen scrubbers and water dryers,
of the highest boiling component in the sample. The use of a
such as molecular sieves, ahead of the instrument to protect the
2 μm to 7 μm frit or packed-screen type filter ahead of the
system’s chromatographic columns. Follow supplier instruc-
sample introduction port is recommended. The valve shall
tions in the use of such gas purifiers and replace as necessary.
provide for a repeatability of at least 2 % relative sample
7.1.1 Hydrogen, 99.995 % minimum purity, <0.1 ppm H O.
volume introduction.
(Warning—Hydrogen is a flammable gas under high pres-
sure.)
6.5 Gas Controls—The GC shall be provided with suitable
7.1.2 Helium, 99.995 % minimum purity, <0.1 ppm H O.
facilities for delivery and control of carrier gas and the detector
(Warning—These materials are flammable and may be harm-
gases. This will consist of the appropriate tank and down-
ful or fatal if ingested or inhaled.)
stream regulators and supply tubing as well as the mass or
pressure controls for the precise regulation of the instrument
7.2 Detector Gases:
operation.
7.2.1 Hydrogen, 99.99 % minimum purity. (Warning—
NOTE 1—Most GC suppliers will provide these devices or recommend Hydrogen is a flammable gas under high pressure.)
the proper supplies.
7.2.2 Air, less than 10 ppm each of total hydrocarbons and
6.6 Column Series/Reversal Switching Valve—If desired, a water. (Warning—These materials are flammable and may be
multi-port valve mentioned may be used to provide the C harmful or fatal if ingested or inhaled.
´1
D2163 − 23
7.3 Reference Standards: sampling, it is strongly recommended that the mixture be
7.3.1 Purity of Reagents—Reagent-grade chemicals shall be contained in floating piston or other cylinders pressurized to at
used in all tests. Unless otherwise indicated, all reagents should least 1380 kPa (200 psi) above the vapor pressure of the
conform to the specifications of the Committee on Analytical mixture at all times (a constant pressure source is suggested).
Reagents of the American Chemical Society where such
8. Preparation of Apparatus
specifications are available. Other grades may be used, pro-
vided it is first ascertained that the reagent is of sufficiently
8.1 Set up the instrumentation in accordance with the
high purity to permit its use without lessening the accuracy of
manufacturer’s instructions or as specified herein.
the determination.
8.2 Install and condition the column according to manufac-
7.3.2 Reference Gas Mixture—Individual and mixed com-
turer’s instructions. See Practice E1510 for recommended
ponent reference materials are commercially available and may
installation and conditioning procedures.
be used to establish qualitative and quantitative calibration.
The calibration standard mixture should be gravimetrically 8.3 Set the GC instrument to the operating parameters.
Allow the instrument to stabilize before proceeding with
prepared, supplied with both gravimetric and calculated volu-
calibration and sample injections. Typical operating conditions
metric concentrations, and certified. Due to the high partial
pressure exerted by methane and ethylene, it is recommended for both PLOT and 100 % dimethylpolysiloxane columns are
provided in Table 2. The conditions provided for the dimeth-
that these components be limited to no greater than 0.2 % by
volume of the mixture composition. It is strongly recom- ylpolysiloxane column are equivalent to those described in Test
Method D6729.
mended that the calibration standards be contained in floating
piston cylinders pressurized to at least 1380 kPa (200 psi)
8.4 Obtain duplicate chromatograms of the standard or
above the vapor pressure of the mixture at all times (a constant
sample, or both. Ensure that none of the peaks obtained have
pressure source is suggested). Common LPG storage cylinders
exceeded the upper range limit of the data-handling device (at
may also be used provided they can be maintained at the
full scale on the data-handling device, all peaks are on scale
required pressure. Liquid mixtures containing levels of each of
and display symmetrical, Gaussian shapes as opposed to flat
the analytes listed in Table 1 in a balance of the type of LPG
peak tops). Peak areas of like components shall agree within
that is being analyzed should be used to calibrate the instru-
2 %. Use the same sample size (split ratio) and range for all
mentation. (Warning—These materials are flammable and
runs. Example chromatograms are provided in Figs. 1 and 2.
may be harmful or fatal if ingested or inhaled.)
8.5 Liquid Sampling Valve (recommended)—Set valve on
7.3.3 Calibration Gas Mixture—A mixture of known com-
and off times to comply with manufacturer’s instructions.
position similar in concentration to the samples being analyzed
may be used to monitor precision and accuracy. For liquid 8.6 Gas Sampling Valve (optional)—Set valve on and off
times to comply with manufacturer’s instructions.
5 8.7 Switching (Back-Flush) Valve (optional)—The valve
ACS Reagent Chemicals, Specifications and Procedures for Reagents and
Standard-Grade Reference Materials, American Chemical Society, Washington, rests in the “off” state, allowing a continuous back-flush flow
DC. For suggestions on the testing of reagents not listed by the American Chemical
through the pre-column. Before or upon injection of the
Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset,
sample, the valve should be rotated to the “on” position so that
U.K., and the United States Pharmacopeia and National Formulary, U.S. Pharma-
the pre-
...