Determination of water- and fat-soluble vitamins in seawater samples by liquid chromatography-mass spectrometry after simultaneous extraction

This manuscript presents the determination of water- and fat-soluble vitamins in seawater samples after being simultaneously extracted in a single solid-phase extraction procedure. The determination of water- (i.e., B 1 , B 2 , B 3 , B 5 , B 6 , B 7 , B 9 , and B 12 ) and fat- (i.e., A (as retinal, retinol, and retinoic acid), D 2 , D 3 , E (as α-, δ and γ-tocopherol), K 1 , K 2 , and K 3 ) soluble vitamins in seawater by liquid chromatography/triple quadrupole mass spectrometry is proposed by two analytical methods. The analytical methods enabled the achievement of low limits of quantification, with values ranging from 0.01 to 0.1 µg kg⁻¹ and of 0.5 µg kg⁻¹ for water- and fat-soluble vitamins, respectively. The analysis was conducted using 1 L of seawater, which was subjected to solid-phase extraction, eluted with 40 mL of methanol, evaporated to dryness and reconstituted with 1 g of methanol. The analysis of both filtered and unfiltered seawater samples was successfully carried out. Therefore, the developed methods allow the determination of water- and fat-soluble vitamins in seawater samples, the latter being determined for the first time. In addition, this provides valuable information for mapping the environmental variability of vitamins in the sea, as well as for consumers of seawater-based food supplements. • Determination of water- and fat-soluble vitamins in seawater • A single solid-phase extraction procedure extracts water- and fat-soluble vitamins • Vitamins determination by liquid chromatography/triple quadrupole mass spectrometry • Raw seawater samples and filtered seawater product have been successfully analyzed. • The filtered seawater product, available as a food supplement, contains vitamins.