Determination of target fat-soluble micronutrients in rainbow trout's muscle and liver tissues by liquid chromatography with diode array-tandem mass spectrometry detection.

This paper describes an analytical approach, based on LC-diode array detector-MS/MS (LC-DAD-MS/MS), for characterizing the fat-soluble micronutrient fraction in rainbow trout (Oncorhynchus mykiss). Two different procedures were applied to isolate the analytes from liver and muscle tissue: overnight cold saponification to hydrolyze bound forms and to simplify the analysis; matrix solid-phase dispersion to avoid artifacts and to maintain unaltered the naturally occurring forms. Analytes were separated on a C analytical column by using a nonaqueous reversed mobile phase compatible with the atmospheric pressure chemical ionization. Compared to other works, the most relevant advantage of the here illustrated method is the large amount of information obtained with few analytical steps: nine fat-soluble vitamins (3,4-dehydroretinol, retinol, cholecalciferol, ergocalciferol, α-tocopherol, γ-tocopherol, δ-tocopherol, phylloquinone, and menaquinone-4) and eight carotenoids (all-trans-lutein, all-trans-astaxanthin, all-trans-zeaxanthin, all-trans-β-cryptoxanthin, all-trans-canthaxanthin, all-trans-ζ-carotene, all-trans-β-carotene, and all-trans-γ-carotene) were quantified after the method validation, while other untargeted carotenoids were tentatively identified by exploiting the identification power of the LC-DAD-MS/MS hyphenation.