Analysis of carotenoids and fat-soluble vitamins in selected plant food by matrix solid phase dispersion followed by liquid chromatography with DAD tandem MS detection

Multi-vitamin determination, especially in unfortified food, is a complex analytical problem because of two main difficulties which make uneasy to find common extraction and chromatographic conditions: the chemical heterogeneity of analytes and their linkage with matrix macromolecular components. For these reasons, the number of publications in this research area is still limited and the official current procedures are based on individual HPLC analysis. Only few works are focused on the concurrent determination of fat-soluble vitamins and carotenoids by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS), either including a limited number of analytes or being based on two different extraction procedures. A LC-DAD-Tandem MS method has been developed for the simultaneous determination of eleven compounds, among fat-soluble vitamins (retinol, α-tocopherol, δ-tocopherol, γ-tocopherol, ergocalciferol, phylloquinone and menaquinone-4) and carotenoids (lutein, zeaxanthin, β-carotene and lycopene), in various foods of plant origin such as maize flour, tomato pulp, green and golden kiwi. Analytes were separated on a C30 reversed-phase column and unequivocally identified by atmospheric pressure chemical ionization (APCI) tandem mass spectrometry. The extraction/clean-up procedure was performed applying the Matrix Solid Phase Dispersion (MSPD) technique with recoveries ranged between 60 and 80%, depending on the matrix selected, and an inter-day precision less than 12%.The coupling of DAD with MS resulted an effective tool for obtaining a qualitative profile of fat-soluble vitaminis and carotenoids occurring in every food, concurrently to the quantitative determination of the target analytes performed by MS detector; moreover, it allowed the carotenoids identification, whose standards are not commercially available. During real samples analysis, menaquinone-4, supposed to have a bacterial origin only, was unexpectedly identified in all foods under study.