GEOCHEMICAL ANALYSIS BY INDUCTIVELY-COUPLED PLASMA OPTICAL EMISSION SPECTROSCOPY USING SLURRY ATOMIZATION

Abstract

Elemental analysis by the nebulization of slurries of geological materials into an inductively coupled plasma has been investigated. High-solids nebulizers, spray chambers and torches have been designed and optimized for aqueous slurry introduction. The influence of particle size on sample introduction and atomization efficiency was shown to be paramount. Kaolin particles greater than 8 um were not atomized in the plasma. When the plasma operating parameters were optimized by simplex only the injector gas flow-rate and viewing height were critical. Clay suspensions of known concentration, varying particle size distributions, and concentration s o f 0.2 to 20% w/v were prepared and major, minor and trace elements determined by slurry atomization. Equivalent atomization efficiencies were obtained for slurries containing particle size of 8 um. For slurries containing larger particles the use of-silicon in the kaolin as an internal standard corrected for variable atomization efficiency. The addition of dispersants greatly increased slurry atomization by decreasing flocculation. Aqueous ammonia (0.35% m/v) was optimal. For high concentration slurries (>8% w/v) nebulization was affected by viscosity and an added internal standard was used to correct this. Slurry atomization was successfully applied to a variety of kaolin analysis and showed promise for on-line monitoring. Dolomite and basalt samples were ground prior to application of the technique, due to problems with dispersion an internal standard correction provided best results. Preliminary investigation of partial dissolution and equal density slurry approaches suggested the former to be more promising.