Spectrophotometric determination of pyridoxine hydrochloride in pharmaceutical samples

Abstract

A spectrophotometric method is described for the determination of pyridoxine based on the formation of an azo dye by the reaction between pyridoxine and diazotised p-nitroaniline followed by reaction of this azo dye with mercury(II) to form a stable complex. Minerals, sugars and several vitamins do not interfere when present in amounts usually found in pharmaceutical preparations. The interference from ascorbic acid was eliminated by its pre-separation as lead ascorbate. The molar absorptivity of the coloured complex is 4.6 × 10⁴ l mol^–1 cm^–1 at 530 nm and Beer's law is obeyed in the range 0–80 µg of pyridoxine hydrochloride. The procedure is simple and rapid and is suitable for the routine determination of pyridoxine hydrochloride.