Geoanalysis using plasma spectrochemistry - milestones and future prospects.

Highlights of plasma spectrochemistry in geoanalysis are reviewed. The techniques are evaluated in terms of recent instrumental developments, calibration strategies, spectral and matrix interferences and analytical performance. While acid decomposition results in solutions containing low salt contents, this decomposition strategy is inappropriate for numerous sample types due to poor recoveries. On the other hand, alkali fusions result in total decomposition, but solutions containing high salt contents constrain the accuracy due to interference effects in the inductively coupled plasma (ICP), the sample introduction system, and in the quadrupole mass spectrometer interface. Therefore, practical limits of determination are evaluated in terms of salt tolerances. It is concluded that ICP-atomic emission spectrometry (AES) is employed mainly for the accurate determination of the major and minor elements and the more abundant trace elements. On the other hand, ICP-mass spectrometry (MS) is used mainly for the determination of trace elements and together with the possibility of obtaining some isotopic information, it profoundly enhances the capability for solving geochemical problems. Several methods of direct solid sample introduction are described. These include direct current (DC) arc emission spectroscopy (DC-AES), slurry nebulization (SN), spark ablation (SA), laser ablation (LA) and glow discharges (GD). These devices allow direct solid analysis of bulk samples, single minerals and inclusions.