Development of GC-MS methods for the analysis of tyre pyrolysis oils

Ngxangxa, Sithandile (2016-03)

Thesis (MSc)--Stellenbosch University, 2016

Thesis

ENGLISH 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.

AFRIKAANSE OPSOMMING : Gas chromatografie in kombinasie met massa spektrometrie (GC-MS) en omvattende twee dimensionele gaschromatografie (GC×GC) metodes is ontwikkel vir die analise van olie afkomstig van die pirolise van afval voertuigbande, bekend as ‘tyre derived oils (TDOs)’. Deur gebruik te maak van GC-MS met óf oplosmiddel terug-ekstraksie, óf vloeistof verdunning vir monstervoorbereiding is 33 vlugtige komponente met die gebruik van standaarde in die olie geïdentifiseer en ‘n verdere 71 is tentatief geïdentifiseer. Die mees prominente verbindings in TDO wat gevind is was dl-limonene, p-cymene, benzothiazole, ethylbenzene, toluene, xylenes, ethyltoluenes and α-terpinolene. Vir die kwantifisering van vlugtige organiese komponente wat markwaarde het is beide die interne standaard metode en standaardbyvoeging gebruik. Die kwantitatiewe data wat verkry is met beide metodes het baie goed ooreengestem, met verskille van tussen 1 en 5%. Om komponente wat in uiters lae vlakke in die TDOs voorkom ook in te sluit, is ‘n selektiewe ion moniterings (SIM) GC-MS metode ingespan om verhoogde sensitiwiteit te kry. Omdat een-dimensionele GC egter dikwels nie daarin slaag om volledige skeiding te bewerkstellig vir die komplekse TDO monsters nie, is GC×GC voorts ondersoek vir die in-diepte analisering van die olies. Om die voordele van die beter skeiding wat GC×GC bied te illustreer, is GC×GC-FID, wat gebruik maak van ‘n nuut-ontwikkelde termiese enkelfase modulator, gebruik vir TDO analise. Vir die verdere identifikasie van die verbindings wat in TDOs voorkom is, is van GC×GC in kombinasie met ‘time-of-flight’ MS (GC×GC-TOFMS) gebruik gemaak. Op hierdie manier is 137 komponente tentatief geïdentifiseer met behulp van hulle massa spektra en retensie indeks data. Die analitiese metodes wat gerapporteer word hou heelwat belofte in vir biede die roetine analise van TDOs.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/98868
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