Tandem mass spectrometry —an additional dimension of chromatography for the determination of biomarkers in fossil fuels

Abstract

A triple-stage quadrupole mass spectrometry (MS) system used in the MS—MS mode with both gas chromatography (GC) and direct-insertion probe as inlet systems, can provide methods alternative to GC—MS for biomarker analyses. Specific parent/daughter ion relationships can be utilized to monitor and resolve classes of biomarkers or individual components in a complex mixture. Furthermore, deuterated analogues of naturally occurring biomarkers can be utilized for quantitation purposes since the parent/daughter relationship for the standard will differ, depending on the number of deuterium atoms present, even though the relative retention times are identical. The utilization of GC—MS—MS and the direct insertion probe MS—MS to determine biomarker distributions in crude oils both qualitatively and quantitatively are discussed in this paper. The results from the study show that it is possible to use the probe data to correlate oils on the basis of their source materials and if necessary select samples for more detailed analysis by GC—MS—MS. A major advantage of the direct insertion probe method is speed of analysis although some component resolution is lost. In an effort to minimize this problem and still maintain the rapid analysis time, the use of short columns in GC is also described. The approach permits relatively rapid analyses with limited chromatographic resolution but at relatively high levels of sensitivity.