Vitamin D and provitamin D in fish

A highly-sensitive high-performance liquid chromatographic method for measuring vitamin D₃ and provitamin D₃ in the edible part of fish was developed. The sample preparation procedure consisted of cold saponification and liquid/liquid extraction of the unsaponifiable matter using a disposable kieselguhr cartridge. For the purification of the sample extracts a semipreparative stage using normal-phase HPLC with UV-detection was applied. A vitamin D and a provitamin D fraction was collected and subsequently quantified by analytical reversed-phase HPLC with electrochemical detection. Internal standardization was used for quantitation. The accuracy of this method was evaluated by recovery experiments. The investigated fish included most of the important fish species consumed in Germany.