Influence of pellet composition in IR-laser ablation inductively coupled plasma atomic emission and mass spectrometry

Aspects of infrared laser ablation as sampling tool for the analysis of pel let materials using inductively coupled plasma atomic emission and mass spe ctrometry have been investigated. The sensitivity for Ca, Fe, La, Mg, Mn, S r, V and Zn in targets prepared from powders of geological reference materi als depends on the kind of additives applied. For understanding this phenom enon the behavior of selected elements was studied. Trace element fractiona tion is prevalently effected by repeated irradiance of a target. There are significant differences in the impoverishing of analytes - as the result of fractionation out of pellets by subsequent laser ablation in dependence on the analytes and their concentrations. The use of an internal standard was studied to reduce the serious problems caused by fractionation. The applic ation of an internal standard is only partly successful for the improvement of the correlation coefficient of calibration plots. The use of suitable b inding materials leads to diminish differences in the ablation behavior of analytes and the internal standard associated with the variation of chemica l and physical properties of the geological matrices. The matched pellets ( SiO2 + carbon + binder) were used to study the influence of the binding of Zn, Bi, Cu, Mn, Fe and Ni on the ablation behavior. The resuits indicate si gnificant differences in the sensitivity when the analytes were added as ox ides, sulfates or in a metallic form. To demonstrate these analyte specific phenomena normalized sensitivity values (sensitivity in laser ablation div ided by sensitivity in pneumatic nebulization) have been used. An explanati on of the analyte specific behaviour has been supported by comparing the no rmalized values with thermodynamic data.