A comprehensive approach for the simultaneous analysis of all main water-soluble vitamins in multivitamin preparations by a stability-indicating HPLC-DAD method.

A stability-indicating HPLC-DAD method for simultaneous determination of all nine main water-soluble vitamins, in addition to two commonly used vitamers, was developed and fully validated in analytical ranges, adjusted to their recommended dietary allowance values. An XSelect CSH C18 column with gradient elution using phosphate buffer and methanol was used for their optimal separation. The results from forced degradation studies along with peak purity tests and response ratios at dual wavelengths for the individual vitamins in all tested samples confirmed the method's stability-indicative nature. The complete developed methodology, including a single sample preparation for the vitamins simultaneous analysis, was applied to their assay in 13 commercial multivitamin preparations, revealing mostly higher amounts than the label claims. The developed method is applicable for stability testing, multivitamin products shelf-life determination as well as routine assay analysis of all water-soluble vitamins in their most common forms, including the analytically most demanding flavin mononucleotide.