A Comparative Evaluation of Methods for the Determination of Vitamin A in Some Fortified Foods
Vitamins are essential for the body, for growth, development, immune system maintenance and ensuring good vision. This study aims at validating some methods for vitamin A analyses and determine its concentration in some fortified foods. Ultraviolet/Visible (UV/Vis) methods, a normal phase High Pressure Liquid Chromatographic (HPLC) method and a reverse phase HPLC method for vitamin A were compared and subsequently used to analyze samples of margarine, edible oil milk and milk drinks purchased from the Abule Egba and Oke Odo market in Lagos State. Two British Pharmacopeia (UV/Vis) methods were compared however; the British Pharmacopeia UV/Vis spectroscopic method that involved extraction in n-Hexane was taken as the validated method. The reverse phase HPLC analyses gave poorly resolved peaks compared with the well resolved peaks in normal phase chromatography for vitamin A; thus it was used to compare with the results of the validated UV/Vis spectroscopic method. Vitamin A concentration for edible oil, milk, margarine, milk drink samples had values in the range of 74,060 IU/ kg to 81,166 IU/kg and 90,445 IU/kg to 1,779,648 IU/kg, 7211 IU/kg to 10,051 IU/kg and 4495 IU/kg to 8450IU/kg, 73690 IU/kg to 80100 IU/kg and 22350 IU/kg to 47490 IU/kg, 218.0μg/100 g to 430.0 μg/100 g and 147 μg/100 g to 673 μg/100 g in the validated UV/Vis method and normal phase HPLC respectively. The results were generally higher than their label claims and may have been due to the overage added during manufacturing.
Keywords: Vitamin A, retinol, fortification, regulation, method development.