Reversed-phase high performance liquid chromatographic determination of rifampin in the presence of its acid-induced degradation products

The determination of rifampin in the presence of its acid-induced degradati on products by reversed-phase high performance liquid chromatography is des cribed. The method was validated as stability-indicating by forced decompos ition of rifampin in acid media. Chromatographic conditions included a Nova -Pak(R) C18 (3.9 x 150 mm, 5 mu m) column and a mobile phase consisting of 0.02M Na2HPO4 and acetonitrile (65:35 v/v), apparent pH 4.5 +/- 0.2 adjuste d by the addition of phosphoric acid. All analyses were done under isocrati c conditions at a flow rate of 1 mL/min and at room temperature. The recove ry average was 99.39% for rifampin. The method was applied to determine rif ampin in commercial capsules and compared with the official method of the U SP XXIII with good agreement between the results.