Liquid chromatographic analysis of vitamin B6 in soy-based infant formula

A liquid chromatographic (LC) method is described for determination of total vitamin B-6 in soy-based infant formula. Total vitamin B-6 is quantitated by using ion-pair LC after precolumn transformation of phosphorylated and free vitamers into pyridoxol. The limit of detection is 0.3 ng and the limit of quantitation is 1.0 ng on-column (injection volume = 100 muL). Linear response ranged from 39 to 616 ng/mL (r(2) = 0.99986). Analysis of a soy-based infant formula control fortified at 6 different concentration levels gave recoveries that averaged 104%. Assay of SRM 1846 gave results within the certified range (8.6 +/-0.086 mg/kg versus the certified value of 8.4 +/-1.0 mg/kg). The method provides a rapid and specific assay for the analysis of total vitamin B-6 in fortified soy-based infant formula.