Determination of fosfomycin in biological fluids by capillary electrophoresis.

A capillary electrophoresis method was developed for the determination of the antibiotic fosfomycin in serum, cerebrospinal fluid and aqueous humor. The technique uses indirect UV detection and the working buffer includes an organic cation to improve fosfomycin mobility. The electrophoretic time of migration is less than 7 min in both fluids. The limit of quantification is 2.5 and 1 microgram/ml in serum and aqueous fluids, respectively (signal-to-noise ratio = 3). The method was validated in serum and water over the concentration range 2.5-200 micrograms/ml. The calibration graph for serum was linear with a correlation coefficient r = 0.999. At a fosfomycin concentration of 2.5 micrograms/ml in serum, the intra- and inter-day precisions (coefficients of variation) were 5 and 5.2%, respectively. The mean recovery in serum was 94.5% (S.D. = 2.4%).