Development and validation of a micellar high-performance liquid chromatographic method for determination of risedronate in raw material and in a pharmaceutical formulation: application to stability studies

A micellar HPLC method was developed for analysis of the antiosteoporosis drug risedronate. The analysis was carried out using a 250 x 4.6 mm id, 5 microm particle size C18 Waters Symmetry column. The mobile phase consisted of 0.02 M sodium dodecyl sulfate + 0.3% triethylamine + 10% n-propanol, prepared in 0.02 M orthophosphoric acid. The pH of the mobile phase was adjusted to pH 6.0, and it was pumped at a flow rate of 0.7 mL/min with UV detection at 262 nm. The method showed good linearity in the range of 2-80 microg/mL, with an LOD of 0.40 microg/mL (1.31 x 10(-6) M) and an LOQ of 1.21 microg/mL. The suggested method was successfully applied for the analysis of risedronate in raw material and a tablet formulation, with average recoveries of 99.91 +/- 1.30 and 101.52 +/- 0.30%, respectively. The stability-indicating capability of the proposed method was proved using forced degradation. By changing the pH of the mobile phase to 4.0, the oxidative degradation product could be separated from risedronate.