CERIMETRIC DETERMINATION OF FOUR ANTIHYPERTENSIVE DRUGS IN PHARMACEUTICAL PREPARATIONS

A sensitive spectrophotometric method is described for the determination of atenolol (ATE), timolol maleate (TIM), captopril(CPL) and diltiazem hydrochloride (DIL HCl) in hulk drugs and in pharmaceutical preparations. The method is based on the oxidation of the studied drugs by a known excess of cerric (IV) in acid medium followed by determination of unreacted oxidant by adding a fixed amount of methyl orange dye (MO) and the increasing in absorbance is measured at 510 nm. In this method the amount of cerium (IV) reacted corresponds to drugs concentration. The experimental conditions were optimized. Regression analysis of a Beer's plot showed good correlation in the concentration ranges of 3.2-6.4, 8.0-18, 3.4-5.2 and 3.6-5.2 mu g/ml for ATE, TIM, CPL and DIL.HCl, respectively. The calculated molar absorptivity values are 5.28x10(4), 3.27x10(4), 6.43x10(4) and 1.12x10(5) L /mol cm, respectively and the corresponding Sandell's sensitivity values are 5.043, 13.2, 3.381 and 4.024 ng/cm(2), respectively. The limit of detection (LOB) and quantification (LOQ) arc reported. No interference was observed from the additives and the applicability of the method was tested by analyzing the pharmaceutical preparations containing the investigated drugs. Statistical comparison of the results with those of official methods shows excellent agreement and indicates no significant difference in precision.