High-performance liquid chromatographic determination of tazobactam and piperacillin in human plasma and urine.

A high-performance liquid chromatographic (HPLC) method with ultraviolet (UV) absorbance was developed for the analysis of piperacillin-tazobactam (tazocillin), in plasma and urine. The detection was performed at 218 nm for tazobactam and 222 nm for piperacillin. The procedure for assay of these two compounds in plasma and of piperacillin in urine involves the addition of an internal standard (ceftazidime for tazobactam and benzylpenicillin for piperacillin) followed by a treatment of the samples with acetonitrile and chloroform. To quantify tazobactam in urine, diluted samples were analysed using a column-switching technique without internal standard. The HPLC column, LiChrosorb RP-select B, was equilibrated with an eluent mixture composed of acetonitrile-ammonium acetate (pH 5). The proposed technique is reproducible, selective, and reliable. The method has been validated, and stability tests under various conditions have been performed. Linear detector responses were observed for the calibration curve standards in the ranges 5-60 micrograms/ml for tazobactam, and 1-100 micrograms/ml for piperacillin and spans what is currently though to be the clinically relevant range for tazocillin concentrations in body fluids. The limit of quantification was 3 micrograms/ml for tazobactam and 0.5 microgram/ml for piperacillin in plasma and urine. Extraction recoveries from plasma proved to be more than 85%. Precision, expressed as C.V., was in the range 0.4-18%.