Liquid chromatographic method for the analysis of all-rac-α-tocopheryl acetate and retinyl palmitate in soy based infant formula using matrix solid phase dispersion

A liquid chromatographic method is described for the analysis of all-rac-α-tocopheryl acetate and retinyl palmitate in soy based infant formula. The vitamins are extracted from infant formula without saponification by matrix solid phase dispersion (MSPD) and quantitated by normal phase chromatography with fluorescence detection. Retinyl palmitate and all-rac-α-tocopheryl acetate are quantitated isocratically with a mobile phase of hexane containing isopropanol @ 0.125% (v/v) and 0.5% (v/v), respectively. Results compared favorably to the label declaration on a retail infant formula product. Recoveries were determined on a soy based zero control reference material (ZRM) fortified with the analytes for soy based infant formula and averaged 99.0% (n=30) for retinyl palmitate and 97.1% (n=25) for all-rac-α-tocopheryl acetate. Five concentrations were examined for each analyte and the results were linear (r2=0.998) over the concentration examined with CV's from 1.24-5.44%. The method provides a rapid, specific and easily controlled assay approach for the analysis of retinyl palmitate and all-rac-α-tocopheryl acetate in fortified soy based infant formula. The cost per analysis at present market value of expendables when using MSPD is between $3-4.00. Considering the escalating cost of manpower, solvents, and hazardous chemical disposal fees, the MSPD technique is efficient and highly cost effective.