Use of solid phase extraction for speciation of selenium compounds in aqueous environmental samples

The performance and optimization of an anion exchanger phase (SAX) in line with a hydrophobic phase (C-18) was studied for the preconcentration of sel enite [Se(IV)], selenate [Se(VI)], dimethylselenide (DMSe), dimethyldiselen ide (DMDSe), diethylselenide (DESe) and diethyldiselenide (DEDe), using a G C-MS system to characterize the different selenium species. Optimum separat ion and preconcentration of the inorganic selenium species were based on th eir retention in an SAX cartridge, with Se(Iv) eluted in 25 ml of 1 mol l(- 1) HCOOH and Se(vr) in 25 mi of 1 mol l(-1) HCl. Organic selenium species w ere retained in a C-18 cartridge and eluted in 2 ml of carbon disulfide. Th e detection limits of the method were 1.4, 1.6, 0.6, 6.0, 400 and 900 ng l( -1) for Se(VI), Se(IV), DMDSe, DEDSe, DMSe and DESe, respectively, using a 1000 ml water sample, and the repeatability was less than 10%. The method w as applied to natural water samples of different origins.