KINETICS AND MECHANISM OF ACIDIC HYDROLYSIS OF NORDAZEPAM STUDIED BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY AND 4TH-ORDER DERIVATIVE ULTRAVIOLET SPECTROPHOTOMETRY

A reversed-phase HPLC method was developed to study the acid-catalysed hydrolysis of nordazepam in hydrochloric acid solutions of 0.01, 0.1 and 1.0 M. One intermediate was observed, which was isolated and ident ified. The mechanism of hydrolysis appeared to be biphasic, showing a consecutive reaction with a reversible first step. Initial breakage of ,the azomethine bond, followed by a slow hydrolysis of the amide bond resulted to creation of the benzophenone product in strongly acidic so lutions. A fourth-order derivative method for monitoring the parent co mpound itself was also proposed and evaluated, as well. Relative stand ard deviation was less than 2% for the HPLC and less than 5% for the d erivative method. Detection limits for nordazepam, intermediate and fi nal degradation product were 1.8 x 10(-9) M, 2.1 x 10(-9) M and 2.0 x 10(-9) M, respectively, in the former method and 7.0 x 10(-7) M for no rdazepam in the latter. Estimation of k(1), k(-1) and k(2) values was tried and results of HPLC and fourth-order derivative methods were com pared. (C) 1998 Elsevier Science B.V. All rights reserved.