Significance and Use
5.1 The hydrocarbon component distribution of gaseous mixtures is often required for end-use sale of this material. Applications such as chemical feedstock 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. Certain regulations may require use of such method.
5.2 The component distribution data of gaseous mixtures can be used to calculate physical properties such as relative density, vapor pressure, and heating value calculations found in Practice D3588. Precision and accuracy of compositional data is extremely important when this data is used to calculate various properties of petroleum products.
Scope
1.1 This test method is intended to quantitatively determine the non-condensed hydrocarbon gases with carbon numbers from C1 to C5+ and non-hydrocarbon gases, such as H2, CO2, O2, N2, and CO, in gaseous samples. This test method is a companion standard test method to Test Method D1945 and Practice D1946 differing in that it incorporates use of capillary columns instead of packed columns and allows other technological differences.
1.2 Hydrogen sulfide can be detected but may not be accurately determined by this procedure due to loss in sample containers or sample lines and possible reactions unless special precautions are taken.
1.3 Non-hydrocarbon gases have a lower detection limit in the concentration range of 0.03 to 100 mole percent using a thermal conductivity detector (TCD) and C1 to C6 hydrocarbons have a lower detection limit in the range of 0.005 to 100 mole percent using a flame ionization detector (FID); using a TCD may increase the lower detection limit to approximately 0.03 mole percent.
1.4 This test method does not fully determine individual hydrocarbons heavier than benzene, which are grouped together as C7+ When detailed analysis is not required the compounds with carbon number greater than C5 may be grouped as either C6+, or C7+. Accurate analysis of C5+ components depends on proper vaporization of these compounds during sampling at process unit sources as well as in the sample introduction into the analyzer in the laboratory.
