Separation and determination of three water-soluble vitamins in pharmaceutical preparations and food by micellar electrokinetic chromatography with amperometric electrochemical detection

A simple, reliable and reproducible method, based on micellar electrokinetic chromatography with amperometric detection, for the separation and determination of the three water-soluble vitamins, namely nicotinamide (VPP), pyridoxine (VB₆) and ascorbic acid (VC), in pharmaceutical preparations and food is described in this paper. A carbon disk electrode was used as working electrode. The optimal conditions of separation and detection were 0.02 mol/l phosphate-0.005 mol/l borate buffer (pH 8.8) containing 0.03mol/l sodium dodecylsulphate (SDS), 7kV for the separation voltage, and 1.20V (versus Ag/AgCl) for the detection potential. The linear ranges were from 3.0 × 10^-4 to 1.0 × 10^-2 mol/l for VPP, 2.5 × 10^-6 to 1.0 × 10^-3 mol/l for VB₆, and 2.5 × 10^-6 to 1.0 × 10^-3 mol/l for VC with regression coefficients of 0.9900, 0.9998 and 0.9990, respectively. The detection limits for VPP, VB₆ and VC were 5.0 × 10^-5, 1.0 × 10^-6 and 1.0 × 10^-6 mol/l, respectively. The method developed in this paper was directly applied to the determination of the three water-soluble vitamins in pharmaceutical preparations and food, and the assay results were satisfactory.