Liquid chromatographic analysis of physostigmine salicylate and its degradation products

A simple stability-indicating HPLC assay has been developed for physostigmine salicylate, capable of following its degradation. A 250 x 5 mm i.d. column packed with 10 microm Bondapak C18 was used, with a mobile phase of acetonitrile - ammonium acetate (pH 6.0; 0.1 M) (50:50, v/v) and flow rate 1.2 ml x min(-1). All peaks are eluted in <10 min and the method has good precision. The optimum wavelength for detection of degradation products is 305 nm. Application of the assay for a commercial preparation of physostigmine salicylate for injection is presented.