Indirect Spectrophotometric Determination of Thiamine Hydrochloride in Presence of Sulphite Via Chromium-1,5-Diphenylcarbazide Complex

A simple, rapid, accurate and precise spectrophotometric method is proposed for the determination of thiamine hydrochloride (Vitamin B1) in both pure form and in its pharmaceutical formulations. The method is based on the oxidation-reduction reaction between vitamin B1 and known amount of chromate CrO4-2 in acidic medium of 2N H2SO4. Then, the excess of chromate is measured via 1,5-diphenylcarbazide which gives a pinkish-violet, water soluble and stable complex and exhibits maximum absorption at 543 nm, with a molar absorptivity of 1.5104 l. mol-1. cm-1, Sandell's sensitivity index of 0.02248 g.cm-2 and a relative standard deviation of 0.31 to 0.57%, depending on the concentration level. Beer's law is obeyed in the concentration range from 0.4 to 40 g. ml-1 of thiamine hydrochloride. The present method has been developed for the determination of thiamine hydrochloride in the presence of sulphite. The proposed method has been applied successfully to the determination of vitamin B1 in pharmaceutical preparations.