A simple, precise, rapid, and low-cost conductometric method for verapamil hydrochloride determination in pharmaceutical formulations is described. Verapamil present in pharmaceuticals containing known quantities of the drug was conductometrically titrated in aqueous solution with silver nitrate using a conductometric cell coupled to an autotitrator. The method is based on the precipitation of chloride ions coming from verapamil hydrochloride with Ag(I) ions yielding AgCl(s) and the conductance of the solution is measured as a function of the volume of titrant. Under optimized experimental conditions the method was applied with success for verapamil determination in three pharmaceutical formulations in the concentration level of 1.00 x 10-2 mol L-1. The relative standard deviation for six successive measurements was smaller than 0.5 % and no interferences were observed in the presence of common components of the tablets such as sodium monophosphate, magnesium stearate and lactose. Recoveries of verapamil from various tablet dosage formulations ranging from 97.1 to 102.8% were obtained. These results are in good accordance with the declared values of manufacturer and an official method based on spectrophotometric analysis.
Keywords: Verapamil hydrochloride, Conductometric titration, Pharmaceutical formulations, HPLC, Capillary electrophoresis, Atomic emission spectrometry, Matrix effect, Precision, Recovery, Selectivity
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