Direct determination of Se and As in solid certified reference materials using electrothermal vaporization inductively coupled plasma mass spectrometry

Firstly, electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) has been successfully applied for the direct determination of Se in solid certified reference materials (CRMs) of both biological and environmental origin. Secondly, in order to exploit one of the most important advantages of ICP-MS (the multi-element capability), Se and As have been determined simultaneously in two CRMs ('Sea lettuce' and 'Estuarine sediment'), the potential of ETV-ICP-MS for accurate mono-element determination of As in solid CRMs having been proven in a previous study. For both the mono-element and the multi-element determinations, several parameters (ashing and vaporization temperature, carrier gas flow rate) have been studied systematically in order to obtain optimized conditions. Both the linearity of the mass response curves and the signal profiles (signal intensity as a function of time) are examined. Absolute detection limits, based on the 3s criterion, are found to be approximately 1 pg. Using single standard addition for calibration and Sb as an internal standard, accurate results are obtained for both the mono-element determinations of Se (mean relative difference with the certified value of 6.5%) and the multi-element determinations of Se and As (mean relative difference with the certified values of, respectively, 6.6% for Se and 7.2% for As).