Simultaneous determination of B-vitamins and ascorbic acid in multi-vitamin preparations by reversed-phase HPLC

The tedious and time consuming methods employed for the analysis of individual B-vitamins can now be replaced by ion-pair reversed-phase high-performance liquid chromatographic (HPLC) methods. This laboratory has previously reported the simultaneous determination of eight water-soluble vitamin standards that is, B1, B2, B6, B12, C, niacin, niacinamide and folic acid. The proposed isocratic HPLC method, employing 3 channels of detection, adequately separated all eight vitamins in less than 20 minutes. This study reports another phase of the project whereby the method was employed for the analysis of pharmaceutical preparations. Different extraction procedures were first evaluated, namely acid, acid plus enzyme and alkaline hydrolysis methods, using vitamin standards, individual vitamin tablets and multivitamin preparations. The amounts obtained from the analysis were compared with the declared values. Recovery studies were also carried out. The method of acid hydrolysis with 0.1N sulphuric acid was found suitable for use and was thus adopted as the extraction procedure for the analysis of 10 multivitamin preparations obtained from various pharmaceutical outlets. For most of these preparations, the amount obtained were close to the declared values, except for folic acid and cyanocobalamin. Further trials on folic acid showed that the problem could be resolved by omitting the filtration step in the final extract after acid hydrolysis and diluting with 0.01N sodium hydroxide before processing for chromatography. Vitamin B12 was not detectable using the present chromatography system probably because of its low concentration in the samples studied.