Capillary electrophoresis with laser-induced fluorescence detection, an adequate alternative to high-performance liquid chromatography, for the determination of ciprofloxacin and its metabolite desethyleneciprofloxacin in human plasma.

A method to determine plasma concentrations of ciprofloxacin and its metabolite desethyleneciprofloxacin (M1) by CE with HeCd laser-induced fluorescence detection is described. Following precipitation of proteins and centrifugation supernatant is injected hydrodynamically (10 s, 0.5 p.s.i.) into the capillary. Overall analysis time for the quantification of both analytes was 7 min. The total amount of plasma needed for multiple injections (n>5) was 10-20 microl. Data on accuracy and precision are presented. The assay performance is compared to the specifications of a validated HPLC method, which is routinely used for the quantification of ciprofloxacin and M1 in body fluids. Both methods showed comparable accuracy and precision for both analytes throughout the whole working range (inter-day precision <9%; inter-day accuracy 96-110%). The limit of quantification (LOQ) of 20 microg/l (M1 10 microg/l) for the CE procedure was slightly higher than for the HPLC method, where 10 microg/l (M1 2.5 microg/l) was determined. However, application of the methods to human plasma samples derived from a clinical study proved that comparable results are obtained and that the sensitivity of the HPCE method was sufficient to fully describe typical plasma concentration time profiles of ciprofloxacin and its metabolite M1. Both the adequate sensitivity and the required smaller sample volume compared to HPLC indicate that the method is feasible for clinical studies where sample amounts are limited, e.g., studies to investigate pharmacokinetics in pediatric patients. Preclinical studies form another possible application of this technique.