Direct atomic spectrometric analysis by slurry atomisation. Part 9. Fundamental studies of refractory samples

Abstract

Fundamental studies of the analysis of refractory slurries by inductively coupled plasma atomic emission spectrometry have identified transport and atomisation effects which may lead to reduced recoveries of analyte elements. When refractory ores containing different minerals are ground, apparently narrow particle size ranges may disguise subtle variations in particle size for different minerals of different hardness. Such samples may then segregate during nebulisation leading to low recoveries for some elements. Experiments using slurries of uniform particle size, cascade impactors and laser diffraction have confirmed the critical importance of particle size. Fine slurries show comparable mass transfer efficiencies to solutions and atomisation efficiency increases as particle size decreases. For difficult samples, e.g., refractory minerals, a particle size of less than 5 µm, with the bulk of the sample below 3 µm would seem to be optimal. It is also shown that a longer travel time in the plasma aids atomisation.