Characterization of crude oils and atmospheric organic compounds by using comprehensive two-dimensional gas chromatography technique (GCxGC)

摘要

This thesis had been given the mandate of applying GCxGC coupled with different types of universal and selective detectors, such as flame ionisation detector (FID), quadrupole mass spectrometer (qMS), time-of-flight mass spectrometer (TOFMS), nitrogen-phosphorous detector (NPD) and electron capture detector (ECD)) for the analysis of various applications, including crude oils, incense smoke, particulate matters and unresolved complex mixtures (UCM). Through the experiments and findings presented in this thesis, it is proven that, once the GCxGC method is fully optimised, it approaches the attributes of the ultimate technique that could potentially provides a complete characterization of crude oil, UCM and many other complex samples, such as smoke generated during the incense burning process. The “inverted-phase” column combination (polar – non-polar) has been employed to provide an alternative and often improved separation in GCxGC. Additionally, it also significantly improves the separation of classes of non-polar compounds, which offers the possibility of facile and rapid oil fingerprinting, as well as sample comparison. A series of biodegraded oils ranging from whole crude oil to heavily biodegraded oils have been investigated by using the polar – non-polar column configuration. The results showed that different classes of compounds hidden under the UCM were separated from each other to form a number of bands on the 2D plot. This technique was also employed for the application of incense smoke with the use of solid-phase microextraction (SPME) as a rapid and simple extraction method for the extraction of volatile compounds in both incense powder and smoke. The results obtained from this study showed that most of the compounds that are emitted into the atmosphere were generated during the combustion of incense. Moreover, various selective detectors, including TOFMS, NPD and ECD were also employed as tools for the analysis of nitrogen-containing and halogenated compounds in incense smoke. Overall, GCxGC has been successfully used as a new innovative tool for close to complete profiling analysis of UCM and incense smoke. This therefore strongly supports the proposal that GCxGC must be the method of choice for the analysis of complex environmental samples.