Advanced Techniques for Organic Analysis

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The research will focus on the advancements in the area of comprehensive multidimensional separations, including gas chromatography (GCxGC) and liquid chromatography (LCxLC), and in passive sampling of volatile organic compounds (VOCs). In the multidimensional realm, the research will aim at developing novel approaches leading to more efficient separations of a variety of samples, from volatile compounds to intact proteins. The main goal of the passive sampling research will be better understanding of the sampler through mathematical modelling, leading to the development of new/improved samplers for a variety of matrices. In GCxGC, we will further explore the pioneering concept of temperature programming of the second dimension (2D). Currently, all GCxGC analyses are carried out by keeping the 2D column at a constant temperature, equal to or higher than that of the main GC oven. This inevitably leads to the general elution problem. We have shown in a preliminary pioneering work that temperature programming in 2D leads to a significant increase in peak capacity. We will further advance this concept by introducing proper temperature control in 2D, as well as reducing the cooling time of the 2D column. The performance of the system will be evaluated using all modulation approaches currently available on the market. We also plan to develop a new modulator combining the best features of flow and thermal modulators and requiring no consumables. In the area of LCxLC, my team and I will promote the use of similar separation mechanisms in both dimensions together with parallel mobile phase gradients. Current thinking is that 2D gradients are necessary to accomplish good orthogonality in LCxLC. We have confirmed through preliminary experiments that with correlated separation mechanisms in both dimensions, parallel gradients produce the best orthogonality and the highest peak capacity. My team and I will test the concept in the separation of intact proteins, which is expected to gain crucial importance in the biopharmaceutical industry. We will seek further improvements in the efficiency of LCxLC separations of proteins through the introduction of thermal modulation based on thermally-responsive stationary phases, characterized by high retentivity at elevated temperatures, and low retentivity at low temperatures. PDMS-based permeation passive samplers developed by my group are being widely used for the characterization of soil gas around the world owing to the fact that they are the only passive soil gas samplers allowing for the determination of analyte concentrations in the gas rather than just the amount collected. My student and I have developed a mathematical model of the sampler allowing better understanding of its performance. This initial model will be developed further to explore potential new applications, including VOC sampling from groundwater. It will also be used to guide the development of a new soil gas sampler based on thermal desorption.