Separation of soluble selenium compounds in different fish species

Sephacryl S-100 was used for systematic studies on soluble selenocompounds in fish. Commonly-eaten species (mackerel, herring, salmon, rainbow trout, eel, cod, plaice, turbot, flounder and dab) were investigated. The mackerel, herring and the flat fish species contained 0.262–0.498 μg Se/g wet weight whereof 23–34% was soluble. Gel chromatography showed that cod, salmon, rainbow trout and eel had most of the soluble selenium (76–88%) in the high-molecular-weight range (>10 kDa). For mackerel and herring, about half of the selenium eluted in the high-molecular-weight range and half in the low-molecular-weight range. All flat fish species contained large amounts of low-molecular-weight selenocompounds with an average apparent molecular weight of 2 kDa. This study shows that there are large differences in selenium distribution among fish species.