Spectrophotometric determination of thiamine hydrochloride using orthogonal polynomials

Abstract

A direct spectrophotometric method for the determination of thiamine hydrochloride in the presence of its degradation products is presented. The method depends upon the use of the combined polynomial method, a modification of Glenn's method of orthogonal functions, to eliminate interferences by degradation products to the absorption spectrum of thiamine hydrochloride. Thus, the coefficient (p_w) of the combined polynomial, P_w, calculated over the wavelength range 226–292 nm at 6-nm intervals, is independent of degradation products, is linearly related to the concentration of thiamine hydrochloride and is reproducible, with a relative standard deviation of 0.13–0.54%. The mean recovery for five mixtures of thiamine hydrochloride with degradation products was found to be 100.1 ± 0.6%. When applied to commercial tablets, the results were in good agreement with the USP fluorimetric method. Further, a graph of logarithm of concentration against time for a solution in borate buffer (pH 10) gave a straight line with a slope of –0.022 6 h^–1, showing that the method may be used to monitor stability.