Simultaneous determination of niacinamide, pyridoxine, riboflavin, and thiamine in multivitamin products by high-pressure liquid chromatography.

A high-pressure liquid chromatographic assay was developed for the determination of four water-soluble vitamins: niacinamide, pyridoxine, thiamine, and riboflavin. The four vitamins are assayed simultaneously in multivitamin products not containing minerals. Thiamine currently is not quantitated in formulations containing minerals because it is not stable under the extraction conditions. The method was applied to the analysis of at least 12 different multivitamin products, including various formulations of sterile products, fluids, compressed tablets, and coated, compressed tablets. The method is stability indicating and is applicable to single-tablet assays.