Determination of fluconazole in human plasma by micellar electrokinetic capillary chromatography with detection at...

The determination of fluconazole (Diflucan) in human plasma by micellar electrokinetic capillary chromatography (MECC) with on-column UV absorption detection at 190 nm from primary, deproteinized and extracted plasma samples is discussed. Direct injection of plain plasma or of the supernatant after protein precipitation with acetonitrile is shown to permit the determination of fluconazole drug levels of > 5 micrograms/ml only. With liquid-liquid extraction employing dichloromethane, the detection limit is about 1 microgram/ml. After extraction using disposable solid-phase C18 cartridges and 1 ml of plasma, however, drug levels as low as 100 ng/ml can be determined unambiguously. Calibration graphs between 0.125-25.0 micrograms/ml (seven data points) are shown to be linear, with a regression coefficient r > 0.999. for fluconazole plasma levels of 5 micrograms/ml, intra-day and inter-day imprecisions (n = 10) are about 2 and 5%, respectively. Using the same solid-phase extraction procedure, 44 fluconazole plasma levels that were determined by MECC are shown to agree well with those obtained by HPLC and elucidated pharmacokinetic data compare well with those found in the literature. The advantages of using MECC instead of HPLC for the determination of fluconazole plasma levels and pharmacokinetics are the high resolution efficiency, low-cost capillary columns and the small consumption of inexpensive and environmentally friendly chemicals.