SLURRY NEBULIZATION INDUCTIVELY-COUPLED PLASMA SPECTROMETRY - THE FUNDAMENTAL PARAMETERS DISCUSSED

Slurry nebulization inductively coupled plasma atomic emission spectrometry (ICP-AES) has been investigated to examine how the particle size distribution of the slurry affects analytical accuracy and precision. An empirical upper diameter for the particle size distribution of a slurry of 2-2.5 mum was derived from the analysis of a range of slurries possessing different particle size distributions. A model for slurry particle transport is suggested that gives good agreement with experimental data. The model assumes that for an arbitrarily defined but realistic standard slurry, the maximum allowable particle size is that which allows the occupation of every aerosol droplet by one solid particle. Theoretical considerations and empirical data suggest that for accurate analyses by slurry nebulization, the particle size distribution of the slurry should not exceed a value, determined by density, of 2.9 mum for a material of density 1 g cm-3 falling to 1.5 mum for a material of density 7 g cm-3. Certain carbonaceous materials were shown to be susceptible to micro-flocculation, resulting in 5-10 member assemblies formed from fine primary particles. This led to transport behaviour and analytical recoveries that would normally be associated with slurries of much coarser particle size. With the required conditions of complete dispersion and the correct particle size distribution, slurry nebulization ICP-AES was applied successfully to a range of certified reference materials using simple aqueous standards for calibration.