RAPID COLUMN LIQUID-CHROMATOGRAPHIC ANALYSIS OF FLUCLOXACILLIN IN PLASMA ON A MICROPARTICULATE PRECOLUMN

A rapid, sensitive, accurate and precise high-performance liquid chrom atographic assay is described for flucloxacillin in plasma. Samples (1 00 mu l) containing dicloxacillin (internal standard) were extracted w ith ethyl acetate (2 ml). The mobile phase of acetonitrile (18%, v/v) in phosphate buffer (0.01 M, pH 7) was pumped at 1.2 ml/min through a 40 x 3.2 mm I.D. column (3 mu m particles). Detection was at 220 nm. C alibration plots were linear (r > 0.9995) from 0.2 to 40 mg/l. Within- day and between-day coefficients of variation were less than 9% (n = 6 ). The detection limit was 0.05 mg/l and the limit of quantitation was 0.3 mg/l. Of 24 drugs tested, only phenytoin and carbamazepine may in terfere in some patients' samples.