The application of differential pulse voltammetry at the glassy carbon electrode to multivitamin analysis

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Abstract
Differential pulse voltammetry at the glassy carbon electrode has been applied to the determination of ascorbic acid, pyridoxine and folic acid in a multivitamin preparation. The individual vitamins all gave well-defined peaks in the anodic region with a linear response of peak current to concentration. The water-soluble vitamins were extracted into aqueous solution and folic acid into dibasic potassium phosphate solution. Before determination of pyridoxine, the ascorbic acid peak was depressed by reaction with formaldehyde. Iron (II) present in the multivitamin preparation did not interfere with the analysis. The voltammetric method compared favourably in terms of accuracy and precision with official methods: it was found to be much simpler, with sample manipulation kept to a minimum. The method was found to be generally applicable to the determination of the vitamins in several multivitamin preparations, or, in simplified form, to the determination of the individual vitamin preparations.