| Summary: | Capillary Electrochromatography (CEC) combines the specificity of high-pressure liquid chromatography (HPLC) with the efficacy of capillary electrophoresis (CE). CEC utilises electrically driven (electroosmotic) flow to drive the mobile phase through a narrow i.d. (typically 50-100 mm) fused silica capillary packed with stationary phase material. Separation of analytes occurs by partitioning between the stationary and mobile phases and by differences in electrophoretic mobilities (for charged molecules). Using electroosmotic flow rather than pressure-driven flow leads to greater separation efficiencies and less band broadening, due to the uniform flow velocity profile produced, as opposed to the parabolic flow profile found with LC. Furthermore, CEC is an ideal chromatographic method to couple with mass spectrometric detection, due to their compatible flow rates. Mass spectrometric detection allows for sensitive analysis and provides substantial structural information. This study commenced with work to understand the theory and practice of offline CEC coupled to UV-Vis detection, using mixtures of corticosteroids as test molecules. Different types of column packings and buffer types were investigated to find optimum operating conditions for CEC. Following this, research into CEC/MS was carried out, firstly using a CEC/MS probe already available, before a CEC inlet, microscopy-MS and nanospray-MS interfaces were designed and constructed. It was important when designing these CEC/MS interfaces to ensure that chromatographic integrity was maintained, to preserve peak efficiency into the mass spectrometer. These CEC/MS devices were evaluated on several mass spectrometers to investigate the limits of detection possible. In addition, offline nanospray, CEC/ESI-MS and automated CEC/MS were carried out to offer a comparison. A number of applications for the new technology were then investigated. Sulfonamide veterinary products were analysed, both as standards in water and then extracted from spiked milk samples. Pharmaceutical products and carbamate pesticides were also tested, the latter extracted from spiked river water samples. The limited sample volumes obtained from a combinatorial library, an ideal application for CEC/MS, were also analysed, along with some biological compounds.
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