Low-pressure liquid chromatography with electrochemical detection for the determination of vitamin A in a multi-vitamin preparation

Abstract

Low-pressure liquid chromatography with electrochemical detection has been applied successfully to the determination of vitamin A in a liquid multi-vitamin preparation. Details of the stationary phase, column and other components are given. A well-jet cell containing a glassy carbon working electrode, operated in the oxidative mode, was used as the detection system. Optimisation of the chromatographic separation was achieved by varying the percentage of methanol in the mobile phase. For one of the columns investigated a mobile phase containing 65% methanol-0.075 M acetate buffer (pH 5.0) gave a retention time of 2.8 min which was suitable for the determination of the vitamin in multi-vitamin samples; the coefficient of variation was found to be 3.8%(n= 10). The recovery of the vitamin was found to be within the manufacturer's specifications. The limit of detection was 300 pg injected (based on a signal to noise ratio of 3 : 1) which is much lower than that expected for vitamin A in pharmaceutical products.