Application of slurry sample introduction to a low-power inductively coupled plasma atomic emission spectrometer incorporating a mini-torch

The use of a low-power ICP (0.65 kW) and a mini-torch (outer tube: 12.6 mm o.d.) for slurry sampling of Al2O3 powders is described. In order to find the optimum conditions for mini-torch ICP-AES, the influence of particle size and aerosol gas flow on the signal intensities was studied. The emission intensities obtained with slurries increased as the particle size decreased and maximized in aqueous solution. The intensities obtained with slurries also increased with aerosol flow rate, but were still smaller than those from solution. The intensity difference between particles of size 0.2–30 μm and solutions increased with increased aerosol flow rate up to a maximum at 0.81 min−1. Dependence of the emission intensity and its relative standard deviation on the pH of the slurries in the mini-torch ICP was also studied. The best signal-to-noise ratio was obtained at pH 3, when the pH of the suspension was varied in the range 1–5. The analysis of JCRM 032 (Japan Ceramic Reference Materials) Al2O3 powders for trace impurities using slurry nebulization under the optimized conditions provided a recovery of Fs> 85% for MgO and Fe2O3 and 67% for Na2O and SiO2, with precision of < 4.3% RSD. The analytical results were also compared with those estimated for the same material, using decomposition method in sealed PTFE vessels at high pressure.