Speciation of selenium in plant water extracts by ion exchange chromatography-hydride generation atomic absorption spectrometry

Determination of selenium ŽSe. speciation in plants is important in studying the bioavailability and toxicity of Se in Se-contaminated soil sediment. In this study, we used an anion exchange resin ŽDowex 1-10X. to separate Se into non-amino acid organic Se, Se-amino acids, selenite ŽSe IV . and selenate ŽSe VI . in a plant ŽStanleya pinnata. extract. The hydride generation atomic absorption spectrometry ŽHGAAS. was used to determine concentrations of these Se compounds in plant extracts. Results showed that Se compounds can be quantitatively separated by the resin column. Recovery of five spiked standard Se compounds Žtrimethylselenonium ion ŽTMSe ., dimethylselenoxide ŽDMSeO., selenomethionine ŽSemet., Se IV and Se VI . in the plant extract ranged from 92.9 to 103%. Water extractable Se accounted for 60.4 72.6% of the total Se in the plant. Among the soluble Se compounds in the plant extract, Se-amino acids were 73 85.5%, Se VI ranged from 7.5 to 19.5% and non-amino acid organic Se was less than 7%. Se IV in most samples was below the detection limit Ž1 g g.. This study showed that considerable amounts of the accumulated Se VI in the plant was metabolized to Se-amino acids during growth of the plant.