Determination of ultra-trace elements in snow samples by inductively coupled plasma source sector field mass spectrometry using ultrasonic nebulization

Trace element analysis of snow samples was performed by inductively coupled plasma sector field mass spectrometry (ICP-SFMS) using ultrasonic nebulization. The mass resolution was set to 3500 in order to use the ability of the high resolution technique to resolve most spectral interferences from the analyte ions. By setting the nebulizer gas pressure at 10 psi, a sensitivity improvement factor of around 40 was observed using the ultrasonic nebulizer in comparison with the standard Meinhard concentric nebulizer. Under these conditions, the sensitivity was 100 MHz per ppm of indium at a mass resolution of 3500, which corresponds to 1 GHz at a resolution of 500. Measurement repeatabilities expressed in terms of RSD were better than 5%, depending on the element. The accuracy of the method was demonstrated by results from runs of certified riverine water reference material SLRS-3 (National Research Council Canada). Trace metal concentrations quantified after analysing calibration standards were measured in snow samples. The detection limits obtained for trace metals in the high resolution mode without the influence of signal interferences were 0.26, 1.4, 0.52, 0.01 ng l(-1) for Mn-55, Ni-58, Cu-63 and U-238, respectively.