Acquisition parameter optimization for single pulse resolved simultaneous LA-Q-ICP-MS multielement analysis

Abstract

In recent years, magnificent developments in laser ablation were achieved regarding ablation cells that enable fast aerosol washout in the millisecond range and thus provide the possibility for high pixel acquisition rates in spatially resolved ICP-MS analyses. However, so far only ToF-ICP-MS can exploit this benefit for fast and spatially resolved multielement analysis. With conventional quadrupole ICP-MS instruments, only one data point for each duty cycle is provided, thus the spatial representation is typically calculated from transient quasi-continuous signals using the scan speed of the laser and predetermined aerosol washout times. Using this conventional approach can lead to errors, such as pixel bleeding, image blur or distortions in case the washout times are not correctly determined or are changing during the analysis of a heterogeneous sample. To circumvent imaging artifacts, single pulse resolved quadrupole ICP-MS acquisition is proposed. While ToF-ICP-MS provides complete m/z coverage for each datapoint of the transient signal of a single laser pulse, multielement analysis in the stated conditions is more complex with sequentially working quadrupole ICP-MS, requiring thoroughly optimized settling and dwell times to the signal duration that is depending on the aerosol washout from single laser pulses. This work explores the framework conditions needed to perform successful multielement analysis in single pulse resolved LA-Q-ICP-MS measurements – preconditions for fast multimodal imaging with absolute spatial correlation. The developed approach is applied for analysis of microplastics using a combined LIBS & LA-ICP-MS instrument, enabling a complete spatial correlation of the information acquired simultaneously with LIBS and ICP MS from single laser shots.