Towards comprehensive analysis of oxygen containing organic compounds in groundwater at a crude oil spill site using GC×GC-TOFMS and Orbitrap ESI-MS

Abstract

In this study, both GC × GC-TOFMS and Orbitrap ESI-MS were used to characterize the oxygen containing organic compounds, OCOCs, present in groundwater at a site where a crude oil pipeline ruptured decades ago. This is the only side-by-side comparison of results from these two methods analyzed by the same laboratory. GC × GC-TOFMS analysis shows OCOCs identified at the crude oil-release site are consistent with, and structurally similar to, those identified at previously studied fuel release sites. Molecular structures close to the release point differ from those found downgradient, becoming less complex and with different compound classes dominating. As with the GC × GC-TOFMS, the Orbitrap revealed that the composition of OCOCs present in groundwater close to the source area was distinctly different from that seen downgradient; however, the chemical structures increased significantly in size and complexity from wells near the source to the farthest downgradient well. Investigation into this finding suggests that the presence and structures of these non-GC-able OCOCs are consistent with organic matter resulting from biosynthesis or other processes found in natural water systems and are unlikely to be intermediates (metabolites) along petroleum biodegradation pathways.