Simultaneous determination of vitamins B2 (riboflavin) and B6 (pyridoxine) in infant formula products by reverse phase liquid chromatography.

An ion pair liquid chromatographic (LC) method is described for the simultaneous determination of vitamins B2 and B6 in infant formula products. The method eliminates many of the UV absorbing ingredients present in the infant formulations. The method involves extraction of the vitamins with distilled water followed by a filtration step and the subsequent analysis of the filtrate by LC. Vitamins B2 and B6 and their vitamers are separated from each other as well as from ingredients in the sample matrix on a 5 microns Spherisorb ODS column. The mobile phase consists of 85% 0.04 M triethylammonium phosphate (pH 3.0), 10% methanol, 5% acetonitrile, and the counter ion, octane sulfonic acid sodium salt. The method is reproducible for both vitamins with relative standard deviations (RSD) ranging from +/- 0.3 to +/- 2.6% depending on the infant formula product. The recoveries of the vitamins from various infant formula products are greater than 97%. The analysis for vitamins B2 and B6 in various lots of infant formula compared well with the official AOAC methods.