Piroxicam quantitation in human plasma by high-performance liquid chromatography with on- and off-line solid-phase extraction

A comparative study of two analytical methodologies for piroxicam quantitation in plasma by off-line and on-line solid-phase extraction (SPE) and high-performance liquid chromatography (HPLC) is described. The SPE cartridges contained C 8 for both extraction methods. The analytes piroxicam and tenoxican (internal standard) were separated on a C 18 column with a mobile phase consisting of acetonitrile:20 m M phosphate buffer pH 3.1 (50:50, v/v) followed by UV detection at 360 nm. The validation of the methods demonstrated good recoveries (over 90%), sensitivity (limits of quantification of 0.05 μg/ml with on-line SPE and 0.1 μg/ml with off-line SPE, based on a 100 μl and 200 μl sample volume, respectively), accuracy and precision (better than 9.5%). Both methodologies have been used for bioequivalence studies.