SPME-multicapillary GC coupled to different detection systems applied to volatile organo-selenium speciation in yeast

In this work the versatility of solid phase microextraction (SPME) in combination with multicapillary gas chromatography (MC–GC) was evaluated using different common detectors for organo-selenium speciation. The methods compared for detection were inductively coupled plasma mass spectrometry (ICP–MS), microwave induced plasma atomic emission spectroscopy (MIP–AES) and atomic fluorescence spectroscopy (AFS). All detectors were found to be suitable, with highest sensitivity being obtained for MIP–AES detection, with detection limits of 0.57 ng ml⁻¹ for dimethyl selenide, 0.47 ng ml⁻¹ for diethyl selenide and 0.19 ng ml⁻¹ for dimethyl diselenide. The method was applied to the determination of volatile alkyl selenides in selenium enriched yeast samples, which revealed that the presence of inorganic selenium gives rise to at least seven different volatile species after metabolization, with dimethyl diselenide the predominant species. Commercial pasteurized yeast, containing mainly selenomethionine for its use as a food supplement, was found to be still active and produces considerable amounts of organoselenium compounds.