Rapid procedure for the determination of vitamins A and D in fortified skimmed milk powder using high-performance liquid chromatography

Abstract

A rapid, high-performance liquid chromatographic (HPLC) method for the determination of vitamins A and D in fortified skimmed milk powder (SMP) is described. Either vitamin D₂ or D₃ is added as an internal standard, depending upon which formulation has been used for fortification, and the sample is saponified and extracted. Vitamin A can be determined directly (without further clean-up) in a portion of this extract using reversed-phase HPLC. Vitamin D is determined on the remainder of the extract after clean-up using a Sep-pak cartridge and the same HPLC system. Details of recoveries of added vitamins and the precision of the method are given.