Application of comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry to biomarker characterization in Brazilian oils

The variety of chemical classes present in oils, as well as possible co-elutions in conventional chromatographic separations, makes the identification of biomarkers a difficult task. Comprehensive two-dimensional gas chromatography (GC × GC) coupled to time-of-flight mass spectrometry (TOFMS) is a powerful tool for overcoming these problems and limitations, since it (i) separates substances using two interconnected capillary columns containing different stationary phases and (ii) uses the fast data acquisition of time-of-flight analyser as a robust registry for GC × GC. In this work, biomarkers present in Brazilian oils were identified both individually and in groups by GC × GC–TOFMS much better than in previous works using one-dimensional GC. In the extracted ion chromatograms (EIC) for ions of mass-to-charge ratio (m/z) 191, co-elutions between tri- and pentacyclic terpanes were resolved in the second column. Noteworthy separation between the C30 hopane and C30R demethylated homohopane was observed. Overlap of hopanes with steranes in the m/z 217 EIC was eliminated. Besides hopanes, demethylated tri- and tetracyclic terpanes were identified and reported for the first time in Brazilian oil samples. These results indicate the superiority of GC × GC–TOFMS as a technique for separation and identification of biomarkers in oils.