Focused microwave-assisted extraction and LC determination of the active ingredient in naproxen-based suppositories

A simple and rapid open-vessel focused microwave-assisted extraction (FMAE) method followed by LC analysis was developed for the determination of naproxen in suppositories. Parameters which might affect the FMAE method, such as nature and volume of the extraction solvent, temperature and extraction time were optimized. The extraction solvent consisted of methanol/sodium hydrogen carbonate (pH 8.7; 0.1 M) (50:50, v/v). Extractions were performed by reaching the target temperature of 70 degrees C in a 7 min linear ramp and then maintaining the target temperature for 3 min. Chromatographic analysis was performed on a Discovery RP-Amide C16 column (250 mm x 4.6 mm i.d., 5 microm particle size). The mobile phase consisted of acetonitrile/potassium dihydrogenphosphate (pH 3.0; 25 mM) (40:60, v/v). The complete analytical procedure was validated with regard to limit of quantification, linearity, precision and accuracy. The advantages of the proposed method in comparison to conventional methods are decreased extraction time, reduced solvent consumption and no further sample clean-up steps required before liquid chromatographic analysis.