Liquid chromatographic determination of the plasma concentrations of cefotaxime and desacetylcefotaxime in plasma of critically ill patients

A method for the simultaneous determination of cefotaxime (CTX) and desacetylcefotaxime (DES) in plasma was developed, using acetonitrile protein precipitation and high-performance liquid chromatography (HPLC) with UV-detection at 285 nm. Desacetylcefotaxime was also analysed after conversion in highly acidic medium to its lactone form (DES-lactone). The chromatographic separation was performed on a C18 Aqua column. The lower limit of quantitation was 1 microg/ml for CTX and 0.5 microg/ml for DES and DES-lactone, using 25 microl of plasma samples. The linearity of the calibration curves was satisfactory as indicated by correlation coefficients of > or =0.990. The within-day and between-day precisions were <12% (n = 18) for the two products and the accuracy was between 88 and 101%. The developed HPLC method was applied for CTX and DES determination in plasma samples of critically ill patients after continuous intravenous infusion of CTX.