MICELLAR ELECTROKINETIC CHROMATOGRAPHY-MASS SPECTOMETRY FOR HIGH SENSITIVE QUANTITATIVE AND QUALITATIVE DETECTION OF NEUTRAL ANALYTES

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Micellar electrokinetic chromatography (MEKC) is a mode of capillary electrophoresis (CE) and is capable of separating neutral analytes by electrophoresis. MEKC is performed simply by adding ionic surfactant to the running solution of capillary zone electrophoresis (CZE) and its separation principle is based on the partitioning of the analytes between the ionic micelle and the surrounding aqueous phase. The presence of the surfactant in the running solution causes problems in mass spectrometric detection, because the significant high concentration of the surfactant deteriorates the ionization efficiency of the electrospray ionization (ESI) interface between CE and mass spectrometry(MS), which is the only one commercially available interface for CE-MS. Several on-line sample concentration techniques have been developed to improve concentration sensitivity in CZE on the basis of the difference in mobilities of the analytes between the discontinuous running solutions in the capillary, but … More these techniques are not applicable to neutral analytes because they do not have electrophoretic mobility. The purpose of this research is to develop techniques for mass spectrometric detection in MEKC as a high sensitive quantitative and qualitative detection method. Another aim of the research is to develop on-line sample concentration techniques if MEKC to improve detection sensitivity in most detection methods. To develop MEKC-MS, a MS instrument equipped with a specially designed atmospheric pressure chemical ionization (APCI) interface, which efficiency is not affected by the presence of significantly high concentration of the surfactant, another new MS instrument equipped with ESI interface were utilized. MEKC-MS was possible for several different analytes if the conditions are optimized by using several techniques, but the technique including instruments must be further developed for easy operation. On-line sample concentration in MEKC was very successful : a new concentration techniques named "sweeping" can enhance the detection sensitivity more than 3 to 5 orders of magnitude in terms of peak heights depending on the affinity of the analytes with the micelle. The combination of the on-line sample concentration techniques and MEKC-MS will be developed to improve the detectability of MS detection. Less