Selenium species and their distribution in freshwater fish from Argentina.
The distribution and speciation of selenium (Se) in freshwater fish (muscle and liver tissue) from lakes in Argentina was investigated. Three introduced species, brown trout (Salmo trutta), rainbow trout (Oncorhynchus mykiss) and brook trout (Salvelinus fontinalis), and one native species, creole perch (Percichthys trucha), were investigated. Values for total selenium in muscle ranged from 0.66 to 1.61 µg/g, while in the liver, concentrations were much higher, from 4.46 to 73.71 µg/g on a dry matter basis. Separation of soluble Se species (SeCys2, selenomethionine (SeMet), SeMeSeCys, selenite and selenate) was achieved by ion exchange chromatography and detection was performed by inductively coupled plasma-mass spectrometry. The results showed that in fish muscle, from 47 to 55% of selenium was soluble and the only Se species identified was SeMet, which represented around 80% of soluble Se, while in the liver, the amount of soluble Se ranged from 61 to 76% and the percentage of species identified (SeMet and SeCys2) was much lower and ranged from 8 to 17% of soluble Se.