Spectrophotometric Determination of Diltiazem Hydrochloride by Its Charge-Transfer Reaction with Chrome Azurol S

Based on the spectrophotometric study on the charge-transfer reaction between diltiazem hydrochloride (DTZ) and chrome azurol S (CAS), a spectrophotometric method for determination of DTZ was proposed. In an ethanol-H2O(1+1) solution, charge-transfer complex with mole ratio of 1∶1 was formed by the reaction between DTZ and CAS, having its absorption maximum at the wavelength of 548 nm. Linear relationship between values of absorbance and mass concentration of diltiazem hydrochloride was obtained in the range of 3.0-60 mg·L-1. Apparent molar absorptivity of the colored complex found was 4.01×104L·mol-1·cm-1. The proposed method was used in the analysis of drug samples of diltiazem hydrochloride tablets giving results of DTZ contents in consistency with values given in literature. Test for recovery was performed by standard addition method using the drug samples as matrixes, giving average recovery of 99.2%.