Direct analysis of solid samples by fs-LA-ICP-MS

Abstract

We review the emerging potential of femtosecond laser-ablation inductively-coupled-plasma mass spectrometry (fs-LA-ICP-MS) for the direct analysis of solid materials. Although LA-ICP-MS has been widely explored and is highly accepted for the determination of major and trace elements, as well as for the measurement of isotope ratios, it still suffers from several limitations that restrain its development as a potential alternative to other, more established techniques. The occurrence of non-stoichiometric effects in the transient signals, defined as elemental fractionation, together with the lack of reference materials for the wide variety of samples of interest often restricts the quantitative analysis to a few elements of identical fractionation behavior. In this sense, significant improvements in the processes responsible for fractionation effects have been recently observed with the use of ultra-short laser pulses. The confinement of pulse energy guarantees better performances in spatial resolution and improves the analytical figures of merit. This review aims to summarize the main differences between the LA mechanisms of short (>1 ps) and ultra-short (<1 ps) laser pulses based on fundamental understanding of the LA process and the most relevant parameters governing the quality of analysis. In order to show the state of the art in fs-LA-ICP-MS, we present a variety of examples for elemental and depth-profiling analysis of solid samples in biological, geological, and materials applications.