OBSERVATIONS ON THE USE OF PELLET DIRECT SAMPLE INSERTION FOR INDUCTIVELY COUPLED PLASMA ATOMIC EMISSION-SPECTROMETRY

The feasibility of analyzing geological materials by the use of the direct sample insertion (DSI) technique into the inductively coupled plasma was assessed with a sediment reference material. PACS-1 (NRCC). Sharp and intense peaks were recorded for elements of high and intermediate volatility (As, Cd, Cu, Hg, Mn, Pb, Se, Sn, Zn) after the insertion of pellets prepared from 1:5 mixtures of PACS-1 in graphite. Probe geometry and plasma RF power were optimized to enhance both the magnitude of the signals and the temporal resolution of spectral overlaps. A variable integration time base was found essential to allow good observation of the signals of analytes ranging from volatile trace level elements to refractory matrix constituents. The use of thermochemical additives to enhance the vaporization of refractory elements was investigated. It was found that chloride releasing reagents were preferable to fluoride salts, because the fluorides caused a sudden massive release of Si into the plasma, which resulted in severe physical and spectral interferences.