Simultaneous determination of flucytosine and fluorouracil in human plasmaby high-performance liquid chromatography

A validated, sensitive and precise reversed-phase high-performance liquid c hromatographic method for the simultaneous determination of 5-flucytosine ( 5-FC) and 5-fluorouracil (5-FU) in human plasma is described. Two compounds , 5-methylcytosine (5-MG) and 5-chlorouracil (5-CU), were used as internal standards for the determination of 5-FC and 5-FU, respectively. Plasma samp les were deproteinized with trichloroacetic acid and chromatographed on an octylsilica column, maintained at 30 degreesC during elution, using a 0.04 M phosphate buffer, pH 7.0, as eleunt. Spectrophotometric diode array detec tion was used at 266 nm. 5-FC, 5-FU, 5-MG and 5-CU were found to have reten tion times of 4.8, 5.8, 7.7 and 11.0 min respectively. Recoveries of 91-120 % with reproducibility and repeatability coefficients of variation of 0.8-6 % were obtained. Mean correlation coefficients of 0.99989 and 0.9995 were f ound for the linear calibration curves (n = 2) of 5-FC (4.816-192.6 mg/l) a nd 5-FU (0.05368-5.368 mg/l), respectively. The limits of quantitation were 0.3 mg/l for 5-FC and 0.05 mg/l for 5-FU. Copyright (C) 2001 John Wiley & Sons, Ltd.