Simultaneous determination of water- and fat-soluble vitamins, lycopene and beta-carotene in tomato samples and pharmaceutical formulations: Double injection single run by reverse-phase liquid chromatography with UV detection

Vitamins and carotenes represent important dietary components essential for health, because of their potential ability to decrease the risk for heart disease, cancer and sight disorders. Established chromatographic methods are typically designed for classes of water- or fat-soluble compounds, based on their different solubility and chemical structures. The simultaneous determination of both kinds of vitamins, in addition to highly lipophilic compounds, such as carotenes, increases the complexity of an analytical method, as well as the choice of proper solubilisation solvents, which must be in tune with the chromatographic eluents. In this study, a novel LC method coupled with UV detection is described for the simultaneous determination of thiamine, riboflavin, niacin, pyridoxine, folic acid, ascorbic acid, retinol, ?-tocopherol, phylloquinone, lycopene and ?-carotene. An on-line focusing step was required for column head trapping of carotenes and fat-soluble vitamins, before injecting the water-soluble vitamins. Then, two consecutive injections, combined in a single run based on a ternary gradient program, allowed an efficient separation of both lipophilic and hydrophilic compounds. The method was validated in terms of linearity, recovery and precision. Detection and quantification limits were in the range 0.6-200 ?g/L and 2-700 ?g/L, respectively. Finally, the potential of the proposed method was confirmed by the analysis of tomatoes and pharmaceutical formulations.