Charge transfer complex formation in spectrophotometric determination of verapamil hydrochloride

Two new spectrophotometric procedures for the determination of verapamil hydrochloride in pure as well as in pharmaceutical preparations were suggested. The methods are based on the formation of C.T. complexes with chromotrope 2B or chromotrope 2R azo dyes followed by extraction in chloroform and measuring the absorbances at 530 and 546 nm, respectively. Linear calibration graphs were obtained in the ranges 4.91-58.93 μg ml^-1 verapamil hydrochloride. Variance coefficients of 1.07-3.85 and 1.09-4.10 were obtained for the verapamil tablets using C2R and C2B, respectively, whereas for the Isoptin tablets, the C.V. values were 1.66-5.08 and 1.89-4.6 using C2R and C2B, respectively. A recovery of 98-108% and 101-109% reflecting 92-99 and 91-99 accuracy % for C2R and C2B, respectively were recorded. Student t-test and F-test statistical treatments were applied for the results obtained by the two methods and compared with the official pharmaceutical method giving excellent agreement with 95% confidence. This elaborates these two methods for safety, accuracy and simple uses for quality control analysis of verapamil hydrochloride in its pure form as well as pharmaceutical preparations.