Browsing by Author "Ngxangxa, Sithandile"
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- ItemDevelopment of GC-MS methods for the analysis of tyre pyrolysis oils(Stellenbosch : Stellenbosch University, 2016-03) Ngxangxa, Sithandile; De Villiers, Andre J.; Tredoux, Andreas; Stellenbosch University. Faculty of Science. Department of Chemistry and Polymer ScienceENGLISH ABSTRACT : Gas chromatography coupled to mass spectrometry (GC-MS) and comprehensive two-dimensional gas chromatography (GC×GC) methods were developed for the analysis of tyre derived oils (TDOs). Using GC-MS with either solvent back extraction or liquid dilution for sample preparation, 33 volatile compounds were identified using standards, while an additional 71 compounds were tentatively identified in TDOs. The most abundant TDO constituents were found to be dl-limonene, p-cymene, benzothiazole, ethylbenzene, toluene, p-xylene, 3-ethyltoluene and α-terpinolene. For quantification of the volatile organic compounds which are known to have market value, both internal standard and standard addition methods were used. The quantitative data obtained from these two methods were comparable differing within ±1-5%. To accommodate some of the compounds occurring in trace amounts in some TDO samples, a selected ion monitoring (SIM) method was also developed for better sensitivity. The developed GC-MS method was validated and demonstrated to be suitable for the quantitative analysis of target compounds in a range of TDOs. Since 1-dimensional (1-D) GC failed to provide complete separation of the complex TDO samples, GC×GC was explored for their in-depth qualitative analysis. As proof of principle, a GC×GC-FID equipped with a novel single-stage thermal modulator was used to demonstrate the benefits of improved separation offered by GC×GC for TDO analysis. For detailed identification, a commercially available instrument fitted with a dual stage cryogenic modulator and hyphenated to time-of-flight mass spectrometer (TOFMS) was used. Analysis of the data obtained on this instrument allowed tentative identification of some 137 compounds using mass spectral and retention index data. The analytical methods reported in this thesis show promise both in terms of the routine quantification of market-value constituents of TDOs, and for the more detailed chemical analysis of these samples.