Spectrophotometric determination of some 1,4-benzodiazepines by use of orthogonal polynomials

A direct spectrophotometric method for the determination of some 1,4-benzodiazepines, namely, nitrazepam, prazepam and dipotassium chlorazepate, in the presence of their degradation products, is presented. The method depends upon the use of orthogonal polynomials, to eliminate interferences by degradation products to the absorption spectra of the intact drugs. The method was proved using synthetic mixtures of the intact drugs with their respective degradation products and its suitability to monitor for the stability of the drugs was demonstrated. The method has been applied to the determination of these drugs in dosage forms, with a coefficient of variation less than 2%.