Quantitative analysis of carbazoles and hydrocarbons in condensates and oils using comprehensive GC–MS/MS and comparative GC–MS analyses

Abstract

Analysis of carbazoles, nitrogen-bearing molecules found in most petroleum fluids, is often limited to GC–MS or GC × GC methods, both of which require prior sample treatment to concentrate components and minimize matrix interference. Recently, workers have introduced a novel method for analysis of carbazoles, using GC–MS/MS, without these required cleanup procedures. In this study, six thermal condensate and crude oil samples are analyzed for carbazoles and other components in their whole-petroleum and fractionated forms by both Selective Ion Monitoring (SIM) and Multiple Reaction Monitoring (MRM) methods to compare the differences. Five additional samples are then analyzed by a new hybrid MRM-SIM mode in a single run measuring over 200 components. We provide a geochemical interpretation of each sample set, based primarily on the MRM-derived carbazole abundance. In addition, we present an updated method for the analysis of carbazoles using GC–MS/MS. This study explores (1) the benefits of a hybrid MRM-SIM method for the analysis of carbazoles and other molecular markers in a single run, (2) surrogate standards to accurately quantify up to 21 species of carbazole molecules, and (3) evidence for the advantage of GC–MS/MS over previous methods for evaluations of thermal condensates and heavy crude oil. Our recommended process for the analysis of carbazole species is whole petroleum analysis using the hybrid MRM-SIM method. Even if unsuccessful with whole petroleum, the analysis of concentrated fractions analyzed on the hybrid MRM-SIM method has advantages over previous methods.