| Summary: | 碩士 === 國立臺灣大學 === 化學研究所 === 96 === In this study, microemulsion electrokinetic chromatography under pH-suppressed EOF was investigated for the separation and on-line preconcentration of six non-steroidal anti-inflammatory drugs, including flurbiprofen, fenoprofen, naproxen, ketoprofen, suprofen and indoprofen. In the precondition process, the absorbance dropped suddenly after applying voltage for a period of time and finally reached a steady state. The absorbance inflection time consisted with the migration time of the microemulsion. Reproducibility and sensitivity were better when the analytes were injected after the absorbance drop. Selectivity and resolution were studied by changing the pH over the range from 2.5 to 5.5 and the variation of the organic modifier, such as acetonitrile, methanol and 1-propanol. The optimum microemulsion background electrolyte solution consisted of 0.8% (w/w) octane, 3.3% (w/w) SDS, 6.6% (w/w) 1-butanol, 5% (w/w) methanol and 84.3% (w/w) phosphate buffer (25 mM, pH 5.5). With an applied voltage of -10 kV, a baseline separation of the drug mixture could be achieved within 40 minutes. Under the optimized conditions, the reproducibility of the retention time, peak height and peak area were less than 5%. The elution order was mainly determined by the hydrophobility of these analytes. In order to enhance the sensitivity, two on-line preconcentration techniques were applied, including ASEI-sweeping and SRMP. Used microemulsion was composed of 0.8% (w/w) di-n-butyl-L-tartrate, 3.3% (w/w) SDS, 6.6% (w/w) 1-butanol, 15% acetonitrile and 74.3% (w/w) phosphate buffer (25 mM, pH 2.5). When ASEI-sweeping was used, the sensitivity which was evaluated by the peak area of flurbiprofen, fenoprofen and naproxen, was enhanced about 280-fold in comparision with normal MEEKC. When SRMP was used, all analytes could be detected simultaneously and baseline separation could be achieved within 30 minutes. The sensitivity which was evaluated by the peak area of all analytes except for indoprofen, was enhanced about 170-fold and the limits of detection were 2~45 μg/L.
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