ASTM D1945-96(2001)
(Test Method)Standard Test Method for Analysis of Natural Gas by Gas Chromatography
Standard Test Method for Analysis of Natural Gas by Gas Chromatography
SCOPE
1.1 This test method covers the determination of the chemical composition of natural gases and similar gaseous mixtures within the range of composition shown in Table 1. This test method may be abbreviated for the analysis of lean natural gases containing negligible amounts of hexanes and higher hydrocarbons, or for the determination of one or more components, as required.
1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
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 and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: D 1945 – 96 (Reapproved 2001)
Standard Test Method for
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Analysis of Natural Gas by Gas Chromatography
This standard is issued under the fixed designation D 1945; 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 (e) indicates an editorial change since the last revision or reapproval.
TABLE 1 Natural Gas Components and Range of
1. Scope
Composition Covered
1.1 This test method covers the determination of the chemi-
Component Mol %
cal composition of natural gases and similar gaseous mixtures
Helium 0.01 to 10
within the range of composition shown in Table 1. This test
Hydrogen 0.01 to 10
method may be abbreviated for the analysis of lean natural
Oxygen 0.01 to 20
Nitrogen 0.01 to 100
gases containing negligible amounts of hexanes and higher
Carbon dioxide 0.01 to 20
hydrocarbons, or for the determination of one or more compo-
Methane 0.01 to 100
nents, as required.
Ethane 0.01 to 100
Hydrogen sulfide 0.3 to 30
1.2 The values stated in SI units are to be regarded as the
Propane 0.01 to 100
standard. The values given in parentheses are for information
Isobutane 0.01 to 10
only.
n-Butane 0.01 to 10
Neopentane 0.01 to 2
1.3 This standard does not purport to address all of the
Isopentane 0.01 to 2
safety concerns, if any, associated with its use. It is the
n-Pentane 0.01 to 2
responsibility of the user of this standard to establish appro-
Hexane isomers 0.01 to 2
Heptanes+ 0.01 to 1
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
2. Referenced Documents
sponding values obtained with the reference standard.
2.1 ASTM Standards:
4. Significance and Use
D 2597 Test Method for Analysis of Demethanized Hydro-
4.1 This test method is of significance for providing data for
carbon Liquid Mixtures Containing Nitrogen and Carbon
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calculating physical properties of the sample, such as heating
Dioxide by Gas Chromatography
value and relative density, or for monitoring the concentrations
D 3588 Practice for Calculating Heat Value, Compressibil-
of one or more of the components in a mixture.
ity Factor, and Relative Density (Specific Gravity) of
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Gaseous Fuels
5. Apparatus
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E 260 Practice for Packed Column Gas Chromatography
5.1 Detector—The detector shall be a thermal-conductivity
type, or its equivalent in sensitivity and stability. The thermal
3. Summary of Test Method
conductivity detector must be sufficiently sensitive to produce
3.1 Components in a representative sample are physically
a signal of at least 0.5 mV for 1 mol % n-butane in a 0.25-mL
separated by gas chromatography (GC) and compared to
sample.
calibration data obtained under identical operating conditions
5.2 Recording Instruments—Either strip-chart recorders or
from a reference standard mixture of known composition. The
electronic integrators, or both, are used to display the separated
numerous heavy-end components of a sample can be grouped
components. Although a strip-chart recorder is not required
into irregular peaks by reversing the direction of the carrier gas
when using electronic integration, it is highly desirable for
through the column at such time as to group the heavy ends
evaluation of instrument performance.
either as C and heavier, C and heavier, or C and heavier. The
5 6 7
5.2.1 The recorder shall be a strip-chart recorder with a
composition of the sample is calculated by comparing either
full-range scale of 5 mV or less (1 mV preferred). The width of
the peak heights, or the peak areas, or both, with the corre-
the chart shall be not less than 150 mm. A maximum pen
response time of2s(1s preferred) and a minimum chart speed
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This test method is under the jurisdiction of ASTM Committee D03 on Gaseous
of 10 mm/min shall be required. Faster speeds up to 100
Fuels and is the direct responsibility of Subcommittee D03.07 on Analysis of
mm/min are desirable if the chromatogram is to be interpreted
Chemical Composition of Gaseous Fuels.
Current edition approved Nov. 10, 1996. Published January 1997. Originally
using manual methods to obtain areas.
published as D 1945 – 62 T. Last previous edition D 1945 – 91.
5.2.2 Electronic or Computing Integrators—Proof of sepa-
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Annual Book of ASTM Standards, Vol 05.02.
3 ration and response equivalent to that for a recorder is required
Annual Book of ASTM Standards, Vol 05.05.
4
Annual Book of ASTM Standards, Vol 14.02. for displays other than by chart recorder. Baseline tracking
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