Spectrophotometric Determination of Vitamin B6 by Coupling with Diazotized p-Nitroaniline

A spectrophotometric method has been described for the determination of pyridoxine hydrochloride (vitamin B6) in pure and pharmaceutical preparations. The method is based on coupling reaction of vitamin B6 with diazotized p-nitroaniline in alkaline solution in the presence of CTAB to form an azo dye which has maximum absorption at 480 nm. Beer's law is obeyed over a range of 5-500 µg/25ml with a molar absorpitivity of 2.7 × 10 4 l. mol 1. cm -1 and Sandell sensitivity index of 0.0076 µg.cm -2 , a relative error +0.22 to + 0.47% and a relative standard deviation of ± 0.11 to ± 0.98%, depending on the concentration level. The proposed method has been applied successfully to the determination of vitamin B6 in pharmactical preparations.