Comparison of different nebulisers and chromatographic techniques for the speciation of selenium in nutritional commercial supplements by hexapole collision and reaction cell ICP-MS

A detailed comparison of the performance of different nebulisation (Meinhard, hydraulic high pressure and microconcentric nebulisers) and chromatographic (reversed-phase and ion-pair) systems for the speciation of selenium by hexapole collision and reaction cell inductively coupled plasma mass spectrometry (ICP-MS) was carried out. The relative limits of detection for the seleno compounds under study (selenite, selenate, selenocystine, selenomethionine and selenoethionine) monitoring isotope Se-80 were in the range 100-200 pg mL(-1) (Meinhard nebuliser), 80- 150 pg mL(-1) (microconcentric nebuliser) and 35-90 pg mL(-1) (hydraulic high pressure nebuliser). Selenium species separation was carried out by both reversed-phase and ion-pair high-performance liquid chromatography (HPLC). More seleno compounds could be separated and a slight improvement in the limits of detection was obtained with the ion-pair HPLC system. Different commercial nutritional selenium supplements were analysed by both chromatographic techniques after extraction with hot water. The efficiency of this extraction was in the range 80-95% for selenate and selenomethionine and 10-25% for selenoyeast-based supplements. Identification of some seleno compounds and quantification in supplement samples were easily and rapidly realised with the MassLynx(TM) software.