Selenium Species Determination in Selenium-Enriched Pumpkin (Cucurbita pepo L.) Seeds by HPLC-UV-HG-AFS

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Pumpkins were treated by spraying the leaves in the flowering period with a water solution containing 1.5 mg Se per liter in the form of Na₂SeO₄. The average total selenium content of seeds was found to be 0.19 µg g^-1 in nontreated pumpkins and 1.1 µg g^-1 in exposed ones. For speciation analysis, enzymatic hydrolysis with different amounts of Protease XIV was carried out. Under optimal conditions of enzymatic hydrolysis, 90% of the total selenium was found in soluble forms. Separation of species was performed using HPLC on anion and cation exchange columns and for detection UV-HG-AFS was applied. In enzymatic hydrolysis extracts, the main fraction of selenium was bound as selenomethionine (SeMet), representing on average of 81 ± 8% of the total Se content in the sample.