Determination of bromazepam and clonazepam in pure and pharmaceutical dosage forms using chloranil as a charge transfer complexing agent

Two new spectrophotometric procedures for determining trace amounts of bromazepam and clonazepam, 1,4-benzodiazepine derivatives in their pure and pharmaceutical dosage forms have been developed. The methods are based on forming C.T. complexes with chloranil in chloroform or ethanol at alkaline pH. The absorbance of the formed C.T. complexes were measured at λ = 330 nm and λ = 375 nm for bromazepam and clonazepam, respectively. Linear calibration curves were obtained in the ranges of 31.6-316.0 μg mL^-1 for bromazepam and of 63.2-316.0 μg mL^-1 for clonazepam. Average recoveries of 99.00-99.60% and 98.57-99.60% were obtained. These reflect 0.5-1.11% and 0.67-1.74% relative errors for bromazepam and clonazepam, respectively. The methods showed standard deviations of 0.6-2.00 and 0.75-1.11 with variance coefficients of 0.63-1.58% and 0.32-1.19% for bromazepam and clonazepam tablets, respectively. Student t-test and F-test statistical treatments were applied for the results obtained by the two methods. t-values indicated the absence of systematic errors at 95% confidence level. Comparing our methods with official HPLC method at 95% confidence level gave insignificant differences. This shows suitability of the two methods for safety, accurate and simple use for quality control analysis of investigated drugs in pure as well as in pharmaceutical preparations.