Determination of δ¹³C of Trace Hydrocarbons in Natural Gas Using Syringe Solid Phase Extraction (SSPE) Coupled with Gas Chromatography/Isotope Ratio Mass Spectrometry (GC/IRMS)

Table 1

Composition and carbon isotopic ratios of the standard sample.

Compound	Formula	δ^13C (V-PDB, ‰) ()	(%)	(%)
Methane	CH4		50.271	0.084
Ethane	C2H6		22.931	0.038
Propane	C3H8		7.013	0.012
Isobutane	i-C4H10		11.284	0.019
Normal butane	n-C4H10		4.418	0.007
Isopentane	i-C5H12		3.352	0.006
Normal pentane	n-C5H12		0.731	0.001

δ¹³C ratios were all measured by direct injection, and all the ratios were calculated by average values of 6 duplicated injections under the same condition. : hydrocarbon content of direct injection (each peak area of the hydrocarbon represents their content); : hydrocarbon content after diluting with helium.