Method modification for liquid chromatographic determination of thiamine, riboflavin, and pyridoxine in medical foods
Chase, G.W.; Landen, W.O.; Soliman, A.G.; Eitenmiller, R.R.
Journal - Association of Official Analytical Chemists 76(6): 1276-1280
1993
ISSN/ISBN: 0004-5756 PMID: 8286968 Document Number: 413720
A reversed-phase ion pair liquid chromatographic method developed for the simultaneous determination of thiamine (B-1), riboflavin (B-2), and pyridoxine (B-6) in perchloric acid extracts of infant formulas was modified to include medical foods. UV detection of B-1 and B-2 was replaced by fluorescence detection, which resulted in improved sensitivity and specificity. B-1 was detected by fluorescence after conversion to thiochrome by a postcolumn reaction with sodium hydroxide and potassium ferricyanide. The method uses a mobile phase of water, acetonitrile, hexanesulfonic acid sodium salt, ammonium hydroxide, and phosphoric acid adjusted to pH 3.6. The column is a 300 times 3.9 mm Nova Pak C-18. Limits of detection were 0.05 mu-g/mL for B-1 and B-2 and 0.01 mu-g/mL for B-6 by fluorescence detection. The system reproducibility was evaluated by completing 10 repetitive determinations on a medical food that gave a coefficient of variation of 5.9, 6.0, and 10.7% for B-1 B-2, and B-6, respectively. Mean recoveries (n = 10) were 111, 96.3, and 113% for B-1, B-2, and B-6, respectively. The results compared favorably with those by AOAC Official Methods 942.23, 940.33, and 961.15 for B-1, B-2, and B-6, respectively.