High-throughput determination of faropenem in human plasma and urine by on-line solid-phase extraction coupled to high-performance liquid chromatography with UV detection and its application to the pharmacokinetic study

An automated system using on-line solid-phase extraction and HPLC with UV detection was developed for the determination of faropenem in human plasma and urine. Analytical process was performed isocratically with two reversed-phase columns connected by a switching valve. After simple pretreatment for plasma and urine with acetonitrile, a volume of 100 μl upper layer of the plasma or urine samples was injected for on-line SPE column switching HPLC-UV analysis. The analytes were retained on the self-made trap column (Lichrospher C18, 4.6 mm × 37 mm, 25 μm) with the loading solvent (20 mM NaH2PO4 adjusted pH 3.5) at flow rate of 2 ml min−1, and most matrix materials were removed from the column to waste. After 0.5 min washing, the valve was switched to another position so that the target analytes could be eluted from trap column to analytical column in the back-flush mode by the mobile phase (acetonitrile–20 mM NaH2PO4 adjusted pH 3.5, 16:84, v/v) at flow rate of 1.5 ml min−1, and then separated on the analytical column (Ultimate™ XB-C18, 4.6 mm × 50 mm, 5 μm).The complete cycle of the on-line SPE preconcentration purification and HPLC separation of the analytes was 5 min. Calibration curves with good linearities (r = 0.9994 for plasma sample and r = 0.9988 for urine sample) were obtained in the range 0.02–5 μg ml−1 in plasma and 0.05–10 μg ml−1 in urine for faropenem. The optimized method showed good performance in terms of specificity, linearity, detection and quantification limits, precision and accuracy. The method was successfully utilized to quantify faropenem in human plasma and urine to support the clinical pharmacokinetic studies.