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 0.03 mol/l sodium dodecylsulphate (SDS), 7 kV for the separation voltage, and 1.20 V (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.