Comprehensive Two-Dimensional Gas Chromatography in Petroleum Derived Samples: A Review on Advances in Source and Weathering Studies of Spilled Oil

Since its introduction comprehensive two-dimensional gas chromatography (GC × GC) has been widely applied to analyze complex samples due to its enhanced peak capacity and selectivity, thereby increasing the number of identifiable peaks and improving coelution issues. Even though it is still undergoing development, GC × GC provides many advantages in the analysis of petroleum-derived samples, whether in reservoir geochemistry applications or in environmental studies associated with spilled oils. In general, it facilitates more thorough fingerprinting and compositional evaluation. In environmental studies, it helps enhance understanding of weathering processes and the environmental behavior of hydrocarbons, as its chromatographic retention indices can robustly estimate liquid vapor pressures, aqueous solubility and other physical chemical properties. This review presents a brief history of GC × GC instrumentation, discussing recent and significant advances in petroleum applications, from data handling techniques to reservoir geochemistry and environmental forensics, as well as some specific advantages achieved and certain limitations that continue to be encountered.

Direct Analysis of Low-Volatile Molecular Marker Extract from Airborne Particulate Matter Using Sensitivity Correction Method

Molecular marker analysis of environmental samples often requires time consuming preseparation steps. Here, analysis of low-volatile nonpolar molecular markers (5-6 ring polycyclic aromatic hydrocarbons or PAHs, hopanoids, and n-alkanes) without the preseparation procedure is presented. Analysis of artificial sample extracts was directly conducted by gas chromatography-mass spectrometry (GC-MS). After every sample injection, a standard mixture was also analyzed to make a correction on the variation of instrumental sensitivity caused by the unfavorable matrix contained in the extract. The method was further validated for the PAHs using the NIST standard reference materials (SRMs) and then applied to airborne particulate matter samples. Tests with the SRMs showed that overall our methodology was validated with the uncertainty of ~30%. The measurement results of airborne particulate matter (PM) filter samples showed a strong correlation between the PAHs, implying the contributions from the same emission source. Analysis of size-segregated PM filter samples showed that their size distributions were found to be in the PM smaller than 0.4 μm aerodynamic diameter. The observations were consistent with our expectation of their possible sources. Thus, the method was found to be useful for molecular marker studies.