On-line solid-phase extraction of piroxicam prior to its determination by high-performance liquid chromatography

A direct method for the determination of piroxicam in plasma is described. Plasma is directly injected onto the extraction column (10 mm x 2 mm I.D., packed with 40-microns Bond Elut C2) where proxicam is separated from the plasma concomitants using a solid-phase extraction procedure. Using a laboratory-made on-line column-switching system, the drug is quantitatively transferred and separated on the analytical column (15 cm x 4.6 mm I.D., Supelcosil LC18 DB, 5 microns) followed by determination using ultraviolet absorption at 331 nm. Validation of the method demonstrated a good recovery (100%), sensitivity (limit of determination 0.2 microgram/ml, based on a 20-microliters sample volume), accuracy and precision (better than 5%). The developed method has been adopted for studying the steady-state pharmacokinetics of the drug.