Determination of cyanocobalamin in multivitamin dietary supplement tablets and infant formulas

HPLC‐UV/MS methods without using off‐line sample clean‐up steps were developed for the determination of cyanocobalamin (Vitamin B12, CN‐Cbl) in multivitamin dietary supplements and infant formulas. Two methods were developed. One used two HPLC columns (an Agilent Zorbax C8 reversed‐phase column and a Waters Symmetry C18 reversed‐phase column) and UV/Vis detection for determination of CN‐Cbl in multivitamin dietary supplements. Because of the low levels of Vitamin B12 in the samples, large injection volumes must be used to exceed the limit of quantitation (LOQ) by UV detection. Due to the large amount of interfering material presented, a switching valve was used to divert most of early eluting interfering materials to waste, an online sample clean‐up without excessive sample preparation steps. The other method used a mass spectrometer as the detector due to the even lower CN‐CBL content existing in infant formulas. The LC/MS method used only 1 column due to the superior selectivity of the mass spectrometer. The LC/MS method can also be used in the analysis of multi‐vitamin dietary supplements. Both methods are specific, precise, and accurate for the intended use. Compared to off‐line sample clean‐up procedures, they offer the advantage of being easier, more economical, and less time consuming.