Status of Methodology for the Determination of Fat-Soluble Vitamins in Foods, Dietary Supplements, and Vitamin Premixes

Fat-soluble vitamins (FSVs) include vitamin A, carotenoids, vitamins D, E, and K. New legislation is being introduced in many countries to reinforce regulatory compliance of declared concentrations of vitamins and other micronutrients in food products and dietary supplements. The levels of FSVs are likely to be more closely scrutinized due to their potential health risks associated with overdosing, in particular of vitamin D. However, a proviso of stricter regulatory compliance is that analytical methods must be fit-for-purpose, providing adequate accuracy and precision. Official methods have been published by organizations such as AOAC INTERNATIONAL, European Committee for Standardization, International Dairy Federation, U.S. Pharmacopeia, and International Organization for Standardization. The methods available for foods, dietary supplements, and vitamin premixes are evaluated in this review. In general, these methods show adequate precision for regulatory compliance; however, the field of application has not often been evaluated for a sufficiently large range of food matrixes. Gaps have been noted in the range of published official procedures, particularly for carotenoids and vitamin premixes. The potential of some recent developments in sample preparation and chromatographic techniques were evaluated to provide improved procedures for FSV analysis in the future.