Comparison of derivative spectrophotometric and liquid chromatographic methods for the determination of rofecoxib

Two different UV spectrophotometric methods were developed for the determination of rofecoxib in bulk form and in pharmaceutical formulations. The first method, an UV spectrophotometric procedure, was based on the linear relationship between the rofecoxib concentration and the λ_max amplitude at 279 nm. The second one, the first derivative spectrophotometry, was based on the linear relationship between the rofecoxib concentration and the first derivative amplitude at 228, 256 and 308 nm. Calibration curves were linear in the concentration range using peak to zero 1.5–35.0 μg · ml^–1. HPLC was carried out at 225 nm with a partisil 5 ODS (3) column and a mobile phase constituted of acetonitrile and water (50 : 50 v/v). A linear range was found to be 0.05–35.0 μg · ml^–1. The developed methods were successfully applied for the assay of pharmaceutical dosage form. The statistics of the analytical data is also presented. The results obtained by first derivative spectrophotometry were compared with HPLC and no significant difference was found.