Submitted to: Experimental Biology
Publication Type: Abstract Only
Publication Acceptance Date: 11/3/2006
Publication Date: 4/1/2007
Citation: Atkinson, R.L., Wolf, W.R. 2007. Determination of Vitamin C in a LC/DAD Method for Analyzing Water Soluble Vitamins in Multi-Vitamin Dietary Supplements Containing Multi-Minerals. Experimental Biology, April 25, 2007, Washington, D.C.
Technical Abstract: We have recently reported a method for the simultaneous determination of a suite of water soluble vitamins in multi-vitamin/multi-mineral dietary supplements (MV/MM) by liquid chromatography with diode array detection (1). This method provided efficient extraction and separation of the Vitamin C, but, quantification was poor due to oxidation of the compound. The extracts rapidly lost detected intensity (within minutes), due to the presence of the multi-minerals in the MV/MM, which catalyzed oxidation of the vitamin C. Standard solutions and extracts of MV tablets without MM were stable. We have successfully modified the conditions of the assay to allow inclusion of Vitamin C in the suite of analytes in this multi-vitamin method. We have rigorously degassed the solvent, lowered the extraction pH to 2.0 from 3.0 and, most importantly added a thermostated sample chamber to the LC autosampler, with the temperature set at 4o C. Under these conditions, Vitamin C was stable for up to 6 hours; sufficient for accurate quantitative determination of the Vitamin C along with the other vitamins. Adding EDTA to the extract to bind the minerals was not helpful in stabilizing Vitamin C, and created more problems with co-eluting peaks for other vitamins. With this method we were able to achieve results for a representative MV/MM dietary supplement table of 63.0 mg/tablet (nominal value 60) with a RSD of 2.4% and recovery of 101% of added vitamin C. 1) Chen P and Wolf WR, Analytical and Bioanalytical Chemistry, 2006 (in press).