Coupling pervaporation-gas chromatography for speciation of volatile formsof selenium in sediments

A method for speciation of dimethylselenide (DMeSe), dimethyldiselenide (DM eDSe) and diethylselenide (DEtSe) in sediments based on a coupling between a pervaporation module, a preconcentration sorptive trap and a gas chromato graph-mass spectrometer is reported. The coupling is performed through a hi gh pressure injection valve which allows two different operational modes: ( a) analysis without preconcentration, in which analytes are directly driven from the pervaporation chamber to the injection port of the chromatograph, and (b) analysis with preconcentration in a trap, in which the analytes fr om the pervaporation chamber are first trapped on a Tenax minicolumn and th en thermally desorbed and driven to the GC. This second approach improves t he sensitivity compared to the direct coupling, reaching estimated absolute detection limits lower than 0.6 ng Se for each tested species. Thc method is applied to the determination of volatile organic selenium species in sev eral sediments collected from different areas in the Southwest of Spain.