An investigation into the development and implementation of multidimensional gas chromatography
Creators: name: Dunn, Michael
Publisher: name: RMIT University
Year: 2024

description: Using a modified Statistical Model of Overlap for MDGC, theoretical models and experimental results were used to assess the benefits, flaws and boundaries of MDGC. The data was then used to directly compare between the two MDGC techniques of tMDGC and GC×GC. The results suggested that the choice of what MDGC technique to apply is critical to the analyses being undertaken. The argument that the more modern and popular GC×GC technique has succeeded tMDGC has no grounds. In fact, GC×GC and tMDGC appeared to be complimentary techniques with tMDGC proving to be more suited for assays requiring quantification and GC×GC more suitable assays requiring qualification. <br><br>During the comparisons between tMDGC and GC×GC, it was found that the auxiliary pressure supplied to a Deans switch located at the union of the <sup>1</sup>D and <sup>2</sup>D could alter the retention times of both the <sup>1</sup>D and <sup>2</sup>D dimensions simultaneously. An increase in the Deans switching pressure would slow the flow of carrier gas on the <sup>1</sup>D while increasing the flow of carrier gas on the <sup>2</sup>D and <i>vice versa</i>. This then led to the notion that for every combination of retention times on the <sup>1</sup>D and <sup>2</sup>D there will be a unique combination of the <sup>1</sup>D inlet pressure and the Deans switching pressure.<br><br>A pressure tuning procedure was developed that once performed can accurately calculate the required <sup>1</sup>D inlet and Deans switching pressures required to achieve a specified <sup>1</sup>D and <sup>2</sup>D retention times. In conventional single column gas chromatography, the adjustment of the pressure drop to accurately reproduce retention times between individual separations is known as Retention Time Locking (RTL). The benefit of RTL is that when a separation is locked to a previous analysis it is possible to identify unknown peaks by cross referencing the retention times. Extensive retention time libraries for a standard method can be used to identify unknown peaks from a locked separation. By successfully applying the pressure tuning procedure to a MDGC system, independent RTL of both columns is achieved. <br><br>Described is a pressure tuning procedure that once performed can accurately calculate the required <sup>1</sup>D inlet and Deans switching pressures required to for a specified <sup>1</sup>D and <sup>2</sup>D retention times. In conventional single column gas chromatography, adjustment of the pressure drop across a column to ensure identical retention times between individual separations is known as Retention Time Locking (RTL). The benefit of RTL is that when a separation is locked to a previous analysis, it is possible to identify peaks by cross referencing the retention times. The then allows for the creation of retention libraries for a standard method that can always be locked too for future identifications. By applying the novel pressure tuning procedure to a MDGC separation, it is possible to independently RTL both columns in a MDGC system and apply the benefits of to RTL to MDGC. This thesis investigates the application of RTL to both the tMDGC and GC×GC techniques. <br>