Active substances of fat-soluble vitamins: Advances in extraction and analysis approaches

Fat-soluble vitamins (FSVs) occur in various active forms, each of which exhibits the biological activity of the respective vitamin and performs the same metabolic functions within the body. The accurate determination of these compounds in food, biological, and pharmaceutical samples is significant for food labeling, treatment/diagnosis of hypo/hypervitaminosis, pharmacological research, and quality supervision of food/drug. In this review, the most recent advances in extraction and chromatographic methods to evaluate active forms of FSVs in various matrices have been discussed and compared. Owing to the recent research trends in the multiform-vitamin assay, particular attention was devoted to the newly established extraction and analytical approaches allowing the simultaneous isolation, separation, and detection of multiple FSV compounds, considering the challenges and their potential solutions. The suitability and specificity of multi-dimensional chromatography-based approaches for FSV substances have been illustrated in detail. Analytical challenges related to mass spectrometry detection of FSV substances have also been briefly discussed.