Thesis (M.Sc. in Pharmacy)--Chulalongkorn University, 1992

A system, involving the combination of non-polar XAD-2 solid phase extraction and isocratic reversed-phase high-performance liquid chromatography, was developed for simultaneous determination of ephedrine hydrochloride codeine phosphate and promethazine hydrochloride. Ethylephedrine hydrochloride was used as the internal standard. The study was performed on five commercial cough-cold syrups. Excellent linearities were obtained over concentration ranges of 40-73 mcg/ml, 48-87 mcg/ml and 20-36 mcg/ml for ephedrine hydrochloride, codeine phosphate and promethazine hydrochloride, respectively. The mean reoveries, averaging recoveries at 3 concentration levels were 99.7, 101.7 and 100.2% for ephedrine hydrochloride, codeine phosphate and promethazine hydrochloride, respectively. The intra-day precision (n=10) and inter-day precision (n=3) of the three days expressed as coefficient of variation were between 1.22-1.86% and 1.37-2.04% respectively. The method was simple, specific, precies and accurate. The oxidative degradation products of promethazine hydrochloride were not found to interfere the procedure.