Laser spot overlap in scanning laser ablation ICP-MS analysis: Impact on analytical signal and properties of the generated aerosol

The aim of this study was to determine whether the degree of pulse overlap affects the analytical response of LA-ICP-MS when utilized in scanning mode. The investigation focused not only on the analytical signal but also on the properties of the generated aerosol and the morphology of ablation craters. Ablation was carried out using a nanosecond ablation system on single-element samples of metals and metalloids, specifically Cr, Hf, Sb, Si, Ta, and W. Pure single-element standards were selected to eliminate elemental fractionation and ensure the chemical composition of the generated aerosol was consistent across all particle sizes. The effect was studied on the surfaces of the samples prepared in various ways, including polished and two types of roughened finishes. It was found that the degree of laser pulse overlap significantly influences the quantity of generated particles, their size, and consequently the measured analytical signal, altering it by tens of percent. Slightly different properties were observed in the groups of metal and metalloid samples. For metals, an increasing overlap of pulses resulted in a decrease in the analytical signal across all types of surfaces. For metalloids, the results were different on polished surfaces. The study shows that adjusting the pulse overlap by combining the scan speed and laser repetition rate can have a significant effect on the LA-ICP-MS analysis results.