Assay of naproxen in rat serum by high-performance thin-layer chromatography/densitometry

A simple, sensitive, and reproducible high-performance thin-layer chromatographic method using densitometry is presented for the determination of naproxen in rat serum. Only 0.1 mL serum was used for extraction. Separations were performed on 10 x 10 cm plates coated with silica gel, with toluene-ethyl acetate-acetic acid (82 + 15 + 3) as the mobile phase. Benzophenone was used as the internal standard. Quantification was performed by densitometry at 260 nm. The response response for naproxen was linear (r = 0.992) over the range 2-100 mg/L. Method validation demonstrated good recoveries (92-96%), sensitivity (limit of quantitation, 1 mg/L), repeatability of sample application (4%), repeatability of the method (8%), and intermediate precision (5%). The procedure was applied to the quantitation of naproxen in rat serum.