Abstract
A simple and efficient method to analyze the volatile and semivolatile organic compounds in crude oils has been developed based on direct immersion solid-phase microextraction coupled to comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry (DI-SPME-GC × GC/TOFMS). A novel fiber, multiwalled carbon nanotubes/hydroxyl-terminated silicone oil (MWNTs-TSO-OH), was prepared by sol-gel technology. Using standard solutions, the extraction conditions were optimized such as extraction mode, extraction temperature, extraction time, and salts effect. With the optimized conditions, a real crude oil sample was extracted and then analyzed in detail. It shows that the proposed method is very effective in simultaneously analyzing the normal and branched alkanes, cycloalkanes, aromatic hydrocarbons, and biomarkers of crude oil such as steranes and terpanes. Furthermore, the method showed good linearity (r > 0.999), precision (RSD < 8%), and detection limits ranging from 0.2 to 1.6 ng/L.
Highlights
As the major components in crude oils, volatile and semivolatile organic compounds have played important roles during petroleum exploration and development
Among the various classes of compounds in crude oil, some biomarkers such as terpanes and steranes are considered as the unique fingerprint of a specific oil and used to determine petroleum system characteristics such as origin, thermal maturity, and biodegradation level, as well as oil-oil and oil-source rock correlations [1]
Most existing analytical methods used to determine these organic compounds in crude oil are conventional one-dimensional gas chromatography coupled to mass spectrometry (1DGC/MS) or tandem mass spectrometry (GC/MS/MS) [2,3,4]
Summary
As the major components in crude oils, volatile and semivolatile organic compounds have played important roles during petroleum exploration and development. Solid-phase microextraction (SPME) is a simple, timesaving, solvent-free, low-cost, and efficient extraction technique, which integrates the extraction, preconcentration, and sample injection into one step [8]. It has gained widespread acceptance in the recent years and has been successfully applied to the extraction and enrichment of trace components in different sample matrices such as foods [9], environmental water or soils [10,11,12], and natural products [13, 14]. Based on the homemade SPME fiber, the volatile and semivolatile organic compounds in crude oils were extracted in DI-SPME mode and analyzed by comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC × GC/TOFMS). An accurate quantitative method was developed for the determination of some important petroleum biomarkers like polycyclic terpanes and steranes and so forth
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