Comprehensive gas chromatography with selective detection techniques for screening of environmental pollutants
Creators: name: Khummueng, Weeraya
Publisher: name: RMIT University
Year: 2024

description: Nowadays, comprehensive two-dimensional gas chromatography (GC×GC) has been acknowledged as a powerful technique for complex sample analysis. Fundamentals of this technique enhance the understanding of complex sample analysis, and contribute to applications in a wide range of samples such as petroleum products, food flavour, perfume, drugs and environmental samples, etc. Several research groups have attempted to study and understand the key elements of GC×GC (the modulator) to explain the modulation process and its modes of operation. Meanwhile, new nomenclature and definitions comprise one aspect of knowledge in GC×GC fundamental relationships. In this thesis, a new terminology called Modulation Ratio (MR) has been added to the list of GC×GC nomenclature. MR has been proposed to provide chromatographers with appropriate choice of modulation period (PM) when GC×GC experiments are carried out. The results show that MR values of 3 to 4 is the preferred value in GC×GC experiments in order to preserve the separation of solutes achieved in the first dimension. Additionally, new operational methods of targeted and comprehensive modes of GC×GC by using the multi-pass loop modulator were investigated. Both the normal set-up, and two looped segments of the capillary column passing through the LMCS modulator, was compared in performance. Both targeted and comprehensive modes, the straight through column segment type, and the two different loop type modulators, were contrasted in the manner in which they permit isolation of regions of the chromatographic band. <br>Two selective detectors, NPD and µECD, were coupled to the GC×GC system for the analysis of environmental pollutants. In this present work, NPD is the detector of choice for the analysis of nitrogen and phosphorus containing compounds. Thus, the analysis of fungicide residues in vegetable samples using GC×GC-NPD was carried out. The unique capability of the GC×GC presentation to show the degradation of a fungicide (iprodione) was demonstrated in this study. The dual detection arrangement which employed both NPD and ECD as parallel detectors (GC×GC-NPD/µECD) for the analysis of multi-class pesticides containing organochlorine pesticides (OCs), organophosphorus pesticdes (OPs) and fungicides (FCs) was conducted. Two deactivated fused silica transfer lines with an equal split ratio connected the output of the second dimension column (2D) via a microfluidic-splitting valve resulted in two simultaneous contour plots visualized from this system. In this context, an opportunity is shown for assigning a detector response ratio (DRR) with the simultaneous response of a solute in the two detectors, as an additional confirmation of solute identity. Likewise, the application of GC×GC-µECD system for the analysis of PCB congeners was performed. The group separation of PCB congeners was achieved with the optimum GC×GC condition. To illustrate the potential of GC×GC-µECD technique as a powerful tool for conducting a group separation of PCB congeners, highly contaminated soil samples were investigated. <br>