Improvements in the GC/MS Analysis of Polycyclic Aromatics in Fossil Fuels: Sampling, Separation, and Assessment.

摘要

The characterization of complex mixtures and accurate quantitation of their components is a challenging endeavor, requiring the application of a powerful analytical technique such as gas chromatography/mass spectrometry (GC/MS). The GC/MS analysis of polycyclic aromatic compounds (PAC) in fossil fuels is particularly difficult due to overlapping retention windows, common spectral ions, and sample matrices rife with interfering compounds. PAC are persistent and harmful, and the fossil fuels that they comprise are the predominant contaminant in thousands of hazardous waste sites worldwide. Accordingly, facilitation of their analysis can have a broad-reaching impact on human and environmental health.;This work describes several lines of research to this end. An in situ sample collection system that provides on-line continuous detection of environmental pollutants was developed; technology that can unambiguously profile organics in the subsurface from ground-level to bedrock. The effects of selected-ion data analysis methods on diagnostic ratios used in environmental forensics were examined, and it was found that methods employing fewer than three ions consistently overestimated alkylated homologue concentrations and led to biased and inaccurate diagnostics. The retention behavior of polycyclic aromatic sulfur heterocycles (PASH) on novel room temperature ionic liquid stationary phases was investigated; these columns can provide improved separation of both polars and nonpolars at higher temperatures than the columns typically utilized for the analysis of fossil fuels. Comprehensive two-dimensional gas chromatography-quadrupole mass spectrometry (GCxGC/qMS) spectra were deconvolved, allowing for the first quantitative analysis of PAC in coal tar by this technique. And a simple and robust modeling technique for estimation of physical properties from GCxGC retention indices was developed. This method was embedded into a software program to produce a component map that provides, for the first time, the ability to assess the weathering of complex mixtures such as crude oil and coal tar by subsurface and sediment environments. In all, the work is relevant to all aspects of the analysis of complex samples: sample collection and preparation, chromatographic separation, data analysis, and utilization of these results in decision-making processes.