Simultaneous quantification of vitamins A, D3 and E in fortified infant formulae by liquid chromatography-mass spectrometry

A novel method for the simultaneous quantification of Vitamins A, D3 and E in fortified infant formulae has been developed using isocratic normal-phase liquid chromatography with positive atmospheric pressure chemical ionization mass spectrometry (LC-APCI-MS). Food products were saponified and the vitamins were extracted by solid-phase extraction (SPE) on a Chromabond XTR cartridge. Quantification of Vitamins D3 and E were performed with Vitamin D2 and 5,7-dimethyltocol (DMT) as internal standards (IS), respectively while no IS was used for Vitamin A. Detection of the vitamins was made in the selected ion monitoring (SIM) mode. MS calibration curves were linear between 0.15 and 12 mg/l for Vitamin A, 5-400 microg/l for Vitamin D3 and 0.25-20 mg/l for Vitamin E with regression coefficient r2 > 0.996 and the limits of detection were below 1.4 ng. The repeatability (CV) obtained on a reference dietetic infant formula was 2.3% for Vitamin A, 2.6% for Vitamin E and 5.9% for Vitamin D3. The between-day variations (CV) over 6 days were in the ranges of 2.4-6.9% for the three vitamins. The mean recoveries from a reference infant formula spiked with all three vitamins ranged from 96 to 105% with a relative standard error less than 9%. The applicability of the method was demonstrated by analyzing a set of infant formula and infant cereals; similar results were obtained with the LC-MS method and reference HPLC methods.