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Investigations into the use of hydrogen addition in the nebulizer gas of an argon inductively coupled plasma (ICP) in an ICP-mass spectrometer for the possible reduction of polyatomic interferences are reported. Hydrogen was found to worsen interferences such as ArO + and ArCl + with respect to an all-argon system. In contrast to these argon-based interferences the levels of MO + were found to be reduced by approximately a factor of 10 with the addition of hydrogen. The hydrogen-argon system was optimized using a simplex procedure. At the defined, optimum the level of CeO + compared to that of Ce + was approximately 0.5%. Detection limits for Gd in 10 μg cm −3 La were 15.9 ng cm −3 in the hydrogen-argon system compared to 2000 ng cm −3 in the all-argon system. These conditions were also used for the analysis of the CRM Bastnasite mill feed ore. IGS 40, using slurry nebulization. The determination of Sm was made possible and the determination of Gd slightly improved by the hydrogen addition. It was concluded that hydrogen addition in an appropriately optimized system offers improvements in heavy rare earth element (REE) determination, in the presence of their lighter counterparts, provided the concentration of the light REE does not exceed μg cm −3 levels.

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 μm 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 μm for a material of density 1 g cm−3 falling to 1.5 μm 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.

Hexafluoroethane (Freon 116), added to the argon nebulizer gas, has been investigated as a potential volatilization aid for refractory materials in slurry nebulization inductively coupled plasma atomic emission spectrometry (ICP-AES). The introduction of Freon 116 resulted in apparently unusual plasma spectrochemistry, which yielded non-linear calibration curves. These were attributed to classical mass action buffering involving highly stable metal fluoride species. This dictated against the use of Freon 116 as a volatilization aid in slurry nebulization ICP-AES.