Stability-indicating HPLC method for simultaneous determination of clidinium bromide and chlordiazepoxide in combined dosage forms.

The study describes development and subsequent validation of a stability indicating reverse-phase high-performance liquid chromatography method for the simultaneous estimation of clidinium bromide (CLI) and chlordiazepoxide (CHLOR) from their combination drug product. Chromatographic separations are performed at ambient temperature on a Phenomenex Luna C(18) (250 mm x 4.6 mm, i.d., 5 microm) column using a mobile phase consisting of potassium dihydrogen phosphate buffer (0.05 M, pH 4.0 adjusted with 0.5% orthophosphoric acid)-methanol- acetonitrile (40:40:20, v/v/v). The flow rate is 1.0 mL/min, and the detection wavelength is 220 nm. The method is validated with respect to linearity, precision, accuracy, system suitability, and robustness. The utility of the procedure is verified by its application to marketed formulations that were subjected to accelerated degradation studies. The method distinctly separated the drug and degradation products even in actual samples. The products formed in marketed tablet dosage forms are similar to those formed during stress studies.