Stability indicating method for verapamil by high-performance liquid chromatography/diode array detector

A stability indicating HPLC procedure for the determination of verapamil in acidic and basic media is described. The samples were analyzed before and after degradation by HPLC with C-18, CN, and phenyl columns. The peak purity of verapamil in each chromatogram was identified by a Diode Array Detector (DAD). A C-18 column using acetonitrile:triethylamine 7.3 mM pH 3.5 (33:67, v/v) as the mobile phase could be employed in chemical stability studies of verapamil. The LOQ was 2.50 μg/mL and the LOD was 0.833 μg/mL. The degradation of verapamil in 3% H2O2 and 0.1 N NaOH solutions were described. They followed second order kinetics model with rate constants of 498.5 and 339.5 M-1hr-1, respectively. The correlation coefficients were greater than 0.99.