Spectrophotometric determination of sulphite and thiamin hydrochloride via Xylenol orange dye


a simple, acurate and rapid spectrophotometric method for determination of sulphite and thiamine hydrochloride (B1) is described. This method used proton transfer reaction between sulphite ion with xylenol orange at pH(7.6) to develop red colour adduct that of maximum absorption at 580 nm. This adduct was used for determination of thiamine hydrochloride by bleaching the red colour product (xylenol orange-sulphite) at the optimum conditions established for the determination of sulphite. Beer’s law is obeyed in the concentration range (10-1000) μg/25ml (i.e. 0.4-40) of sulphite and 10-2000, μg/25ml (i.e. 0.4-80) for thiamine hydrochloride at the selected wavelength, the molar absorbtivity 2.8×104 l.mol-1.cm-1 for SO32- and 2.69×104 l.mol-1.cm-1 for thiamine hydrochloride, Sandell's index for sensitivity 0.002857 μg .cm-2 for sulphite and 0.012537 μg .cm-2 for B1. Good recoveries of sulphite and thiamine hydrochloride from water samples and pharmaceutical formations are achieved using the proposed method.