Volatile organo-selenium speciation in biological matter by solid phase microextraction-moderate temperature multicapillary gas chromatography with microwave induced plasma atomic emission spectrometry detection

Microwave induced plasma atomic emission spectrometry (MIP-AES) in combination with multicapillary (MC) gas chromatography could be proven to be useful for element specific detection of volatile species. Solid phase microextraction (SPME) was used for preconcentration and sample-matrix separation. The fiber desorption unit as well as the heating control for the MC column were in-house developed and multicapillary column was operated at moderate temperatures (30-100 °C). The method was optimized for organo-selenium species (dimethylselenide (DMSe), diethylselenide (DEtSe) and dimethyldiselenide (DMDSe)), using a chemometric approach. Stationary phases for the separation column were optimized using a conventional GC and contrasted with the results obtained with the MC. Application was focussed on selenium accumulating biological matter, such as lupine, yeast, Indian mustard and garlic. These samples were grown in hydroponic solution containing inorganic selenium (Na₂SeO₃ and Na₂SeO₄). SPME sampling was carried out in fixed volume flow boxes in headspace above the living plants and in vials using treated samples. Results demonstrate inorganic selenium transformation into volatile organic species during metabolism. Separation is fast, a chromatogram can be obtained in less than 3 min and detection limits were at sub-ppb level for all investigated species. The system is independent from the use of a conventional gas chromatographic oven and can be used as a versatile alternative to highly cost intensive methods such as GC-ICP-MS.