A study of solid sample introduction methods for inductively coupled plasma spectrometry

The development of sample introduction techniques for solid materials is a desirable goal in analytical atomic spectrometry. Traditional techniques have involved the introduction of samples as liquids by processes such as nebulisation. However some solid materials are not readily amenable to dissolution procedures and for the determination of elements at the ultra-trace level the reagents used for dissolution may produce undesired contamination. An additional problem for such determinations is that the dissolution process- may dilute the sample below the level which can be measured by the selected technique. The relative merits of three techniques for the introduction of solids for inductively coupled plasma optical emission spectroscopy (ICP-OES) and inductively coupled plasma mass spectrometry (ICP-MS) have been evaluated in this thesis. The techniques studied were a laser ablation system based on a Nd:YAG laser, slurry nebulisation and an electrothermal vaporisation (ETV) system. The parameters which affect the performance of these techniques have been discussed. The application of each technique to the analysis of some geochemical samples has been described. Results are presented for the determination of various elements in fly ash and standard rock samples. The results obtained for each technique are compared. A value of merit has been defined to allow comparison of the results in this thesis with results published in the literature. A comparison of the plasma source in the presence and in the absence of water has been included in this thesis. Ionisation temperature and electron number density measurements were made usinq traditional nebulisation and compared to those obtained using laser ablation.