Quantification of the C30+ fraction of North sea gas condensates by high temperature capillary gas chromatography

Abstract

Good reproducibility and quantitative analysis of high molecular mass n-alkanes by high temperature capillary gas chromatography (HTCGC) is attainable. For the authentic n-alkanes, the method described in this paper gave for C₂₀–C₆₀, an s_r of under 5% for manual injection, a linear response factor and a linear calibration over the concentrations used. When applied to the analysis of two waxy North Sea gas condensates, n-alkanes with carbon numbers extending above C₈₀ were observed. This is a surprising result because condensates are generally low molecular mass fluids similar to gasoline. Good quantitative agreement was observed between HTCGC and conventional gas chromatography for carbon fractions less than C₃₀ but HTCGC was able to extend the quantitative analysis to carbon numbers of at least C₆₅.