Multi-element analysis of melt and fluid inclusions with improved detection capabilities for Ca and Fe using laser ablation with a dynamic reaction cell ICP-MS

Abstract

Analysis of melt and fluid inclusions by laser ablation inductively coupled plasma mass spectrometry has contributed significantly to our understanding of magmatic and hydrothermal processes. The combination of laser ablation and ICP-MS detection allows the quantification of a wide variety of elements in inclusions as small as 10 µm. The transient nature of the signal and the low amount of sample material have maintained quadrupole based ICP-MS as the instrumentation of choice, due to high sensitivities combined with fast sequential detection capabilities. However, the detection of some elements was limited due to polyatomic and isobaric interferences. Recently introduced dynamic reaction cell technology offers the reduction of interferences commonly found in ICP-MS and thus the determination of important elements with improved signal to noise ratio. The capability of a dynamic reaction cell for multi-element analysis with short transient signals was studied for the simultaneous determination of major, minor and trace element concentrations in single fluid and melt inclusions. Analyses performed with the dynamic reaction cell were compared with results obtained in the standard mode operation of the ICP-MS. The results show that the reaction cell is well suited for fast transient multi-element analysis, providing very comparable results to the standard mode. Hydrogen has been found efficient for removing Ar+ and Ar-based polyatomic ions from the mass spectrum when a buffer gas is added to enhance thermalization of the ions. Due to this, the limits of detection for Ca were improved by 2.5 orders of magnitude and a factor of 20 for Fe using the most abundant isotopes for analysis.