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)

Sample preparation technique, for the analysis of δ13C ratios in oil and gas samples, has gradually been recognized as one of the most crucial steps of the whole analytical process. In this study, a new convenient method, syringe solid phase extraction (SSPE), was proposed for measuring δ13C in natural gas samples. Based on conditional experiments of temperature and time, SSPE fitted with activated carbon adsorbent was applied with a gas chromatography/isotope ratio mass spectrometry (GC/IRMS) system for trace carbon isotope analysis. The results showed that isotopic fractionation was not clearly observed during the adsorption and desorption process, and the δ13C ratios measured by SSPE-GC/IRMS were in good agreement with the known δ13C ratios of CH4~C5H12 measured by GC/IRMS with the accuracy all within ±0.48‰. A natural gas sample was applied to verify the efficiency of this new method, and the obtained results confirmed that SSPE-GC/IRMS is a reliable technique characterized with simplicity, efficiency, and reliability.