Spectrophotometric Determination of Thiamine hydrochloride Via Oxidative Coupling Reaction Using 4-Aminoantipyrine


A sensitive spectrophotometric method has been developed for the determination of thiamine hydrochloride by oxidative coupling reaction of thiamine with the reagent 4-aminoantipyrine (4-AAP) in the presence of copper sulphate as oxidizing agent in alkaine medium forming a reddish brown colour. The product show maximum absorption at 335 nm. The molar absorptivitiy is 26410.59 l/mol.cm for concentrations obeyed Beer’s law in the range 0.2-18 μg.ml-1. The recovery was 100.93 % with relative standard deviation < 2.0 % for thiamine hydrochloride.Thiamine and reagent 4-AAP product was formed in the ratio of 1:1. The stability constant of the product was 3.39×106 l.mol-1 for thiamine hydrochloride indicating the good stability of this product. The optimum conditions for full colour development are described and the proposed method was applied successfully for determination of thiamine in the pharmaceutical preparation (Neurorubine). The common excipients used as additives in pharmaceutical do not interfere in the proposed method.