Separation of thia-arenes and aza-arenes from polycyclic aromatics in snowpack samples from the Athabasca oil sands region by GC×GC/ToF-MS

Abstract

ABSTRACTComprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC/ToF-MS) was used for the analysis of thia-arenes and aza-arenes in standard mixtures containing 45 polycyclic aromatic compounds (PACs), and in the aromatic fraction of snowpack samples collected from the Athabasca oil sands area of Alberta, Canada. The GC columns used included a shape-selective liquid-crystalline stationary phase (LC-50) and a high-polarity ionic-liquid stationary phase (SLB-IL60), both in the first dimension. A fast diffusion and low-polarity nano-stationary phase (NSP-35) and a mid-polarity stationary phase (Rxi-17), were used in the second dimension, respectively. Both configurations showed good repeatability for retention times in the first and second dimensions, peak areas and peak heights. Instrument detection limits ranged from 0.5 to 10 pg µL−1 for both configurations. In general, the LC-50×NSP-35 configuration favoured the separation of isomeric compounds by using more of the 2D chromatographic space available (>80%), particularly for compounds with molecular mass >160 u. Therefore, LC-50×NSP-35 was recommended for the analysis of thia-arenes and alkylated PAHs in environmental samples collected from the oil sands area. Alternatively, the SLB-IL60×Rxi-17 configuration favoured molecular similarity grouping over isomer separation. This was observed for a group of aza-arenes (i.e. carbazoles, benzo[a]carbazoles and alkylated-derivatives), which were resolved from other PACs and from the sample matrix. The risk of false positives and overestimations in the analysis of thia-arenes, aza-arenes and alkylated PACs in one-dimension GC/MS was explored and further reduced by using GC×GC/ToF-MS with LC-50×NSP-35 and SLB-IL60×Rxi-17.