Spectrophotometric determination of some drugs containing phenolic group using 3-methyl-2-benzothiazolinon hydrazone hydrochloride [MBTH]

ABSTRACT

A simple, rapid, sensitive and suitable method for analysis of etilefrineHCl [I], hexoprenaline.HCl [II], levodopa [III] and carbidopa [IV] either in pure form or in pharmaceutical formulations is described. The proposed method is based on an oxidative coupling reaction with 3-methyl-2-benzothiazolinon hydrazone hydrochloride [MBTH] in the presence of an oxidant [Ce+4 or F e+3] to give coloured species. The resulting coloures are well developed within 5 minutes at 20 +/- 5°C and stable for at least 2 hours. The gamma max were 517, 477 and 474 nm for I, II, both III and IV, respectively. A linear correlation was found between the absorbance and the concentration. Beer's law was obeyed for concentration ranges from 1-7 mg/ml, l-ll mg/ml, 1-8 mg/ml and 2-24 mg/ml for I, II, III and IV, respectively. The molar absorbtivities and Sandell sensitivities were calculated. The results of analysis of pure drugs by the proposed method are in good agreament with the official BP and USP methods. The results obtained showed recoveries of 99.80 +/- 0.27, 100.40 +/- 1.26, 99.89 +/- 0.21 and 99.96 +/- 0.36 for I, II, III and IV, in order. The proposed method was successfully applied to determine the studied drugs in their pharmaceutical dosage forms