FIRST-DERIVATIVE SPECTROPHOTOMETRIC AND HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC DETERMINATION OF CINCHOCAINE HYDROCHLORIDE IN PRESENCE OF ITS ACID DEGRADATION PRODUCT

Two methods are presented for the determination of cinchocaine HCl in presence of its acid-induced degradation product using first (D-1) der ivative spectrophotometry and high-performance liquid chromatography. Cinchocaine HCl was determined by measurement of its first derivative amplitude at the zero crossing point of 2-hydroxyquinoline-4-carboxyli c acid diethylaminoethylamide as its acid degradation product (at 333. 5 nm). The HPLC method depends upon using a mu Bondapak C-18 column at ambient temperature with a mobile phase consisting of acetonitrile-0. 01 M sodium acetate trihydrate (45:55, v/v) containing 0.06% (w/v) hep tane sulphonic acid sodium salt and adjusted to apparent pH 4.5 with a cetic acid at a flow rate 2 ml min(-1). Quantitation was achieved with UV detection at 254 nm based on peak area. The HPLC method was applie d for simultaneous determination of cinchocaine HCl, methylparaben and propylparaben. The two proposed methods were successfully applied to the determination of the cinchocaine HCl in laboratory-prepared mixtur es in the presence of its acid degradation product and in cream. Moreo ver, the proposed methods were utilized to investigate the kinetics of the acid degradation process at different temperatures and the appare nt pseudo first-order rate constant, half-life and activation energy c alculated. (C) 1998 Elsevier Science B.V. All rights reserved.