Attenuation of spectral interferences during laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) using an rf only collision and reaction cell

Abstract

The reduction of spectral interferences in laser ablation inductively coupled plasma mass spectrometry was investigated using an rf only hexapole as a collision and reaction cell with H₂ as the reaction gas and He as a buffer gas. Argon-based polyatomic ions (ArX⁺) were attenuated by between 1 and 6 orders of magnitude with H₂ during laser ablation experiments whilst analyte transmission under the same parameters was maintained above 80%. The amount of ArX⁺ attenuation for a fixed volume of reactive H₂ gas was proportional to the electronegativity of parent element X. Interferences were not significantly attenuated with He. However, a change from ‘dry’ to ‘wet’ conditions in the plasma led to reactions with water molecules in the cell giving an apparent reactivity for clean He buffer gas whilst reducing the efficiency of some reactions with H₂. Improved accuracy and precision were demonstrated under optimised conditions for the analysis of trace elements in sulfide and carbonate standard reference materials as a result of background interference reduction. Multi-element analysis was possible with reactive gases in the reaction cell as demonstrated by the accurate analysis, to within 15% of the recommended values for most trace elements, of candidate glass reference materials using NIST SRM glasses for calibration.