Aerosol entrainment and a large-capacity gas exchange device (Q-GED) for laser ablation inductively coupled plasma mass spectrometry in atmospheric pressure air

Abstract

A new gas exchange device (Q-GED) that allows a carrier gas flow of 0.8 L min⁻¹ atmospheric air to be exchanged with Ar combined with aerosol entrainment applied to the analysis of large or heterogeneous samples using Laser Ablation (LA) is reported. The exchange of air components with Ar in the Q-GED was tested using GC-TCD and ICPMS. In ICPMS, no change in oxide levels, or gas blanks, was observed, suggesting a complete exchange of air with Ar. Measured sensitivities were in the same range as sensitivities obtained using LA with an Ar atmosphere, however, the sensitivities were approximately 2-fold lower than those obtained when ablating in He. It was demonstrated that particle transport efficiencies can be enhanced when using quasi-closed cell approaches to control and influence the aerosol expansion volume. Therefore, a plume entrainment device was designed and optimized by computational fluid dynamics, produced using rapid prototype printing, and applied to LA-QGED-ICPMS. Quantitative multi-element analysis of various geological glass reference materials is reported using NIST SRM 612 as the external calibration standard, with relative differences to preferred values of less than 15%. No additional temporal signal dispersion was observed when comparing the new setup with closed cell approaches when using the same flow rates. As opposed to the former GED I-type, a higher spatial resolution can be obtained without destructive sample preparation for large-scale stalagmites. In a proof of concept, it was shown that the same concentration variations were detected for closed cell and GED-based approaches in large-scale stalagmites.