When Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) is used for multi-elemental quantification, matrix-matched reference materials are required, to circumvent the challenge of matrix dependent effects during the ablation process, which influence the accuracy of stoichiometric ratios within the sample.

In 1998, Todolí et al. showed that during the process of laser ablation of polymers, gaseous species are formed during the ablation process. [1] Based on this finding, Frick et al. provided experimental evidence in 2012, that the formation of gaseous carbon species correlates to the oxygen content of the investigated sample, which prevents the use of carbon as internal standard for quantitative analysis. [2] The topic was revisited recently by Van Helden et al. in 2024 [3], where the formation of gaseous species for various elements was reported when ablating doped gelatine calibration material. In contrast, glass standards did not show any evidence for such gas phase formation. These studies are based on the usage of lasers with a pulse width in the ns range. However, it has been demonstrated in various studies over the past years, that the mechanism underlying the laser-matter interaction differs significantly when using a laser with pulse widths in the fs range. [4] How much the pulse width would influence the gas phase formation is currently unknown and was the subject of this project.

This study investigates the formation of gaseous species, with particular focus on the elements carbon and sulfur, when using ns and fs laser ablation. The experiments utilize a Gas Exchange Device (GED), which separates gaseous components from particulate matter, along with a Millipore filter with a pore size of 0.2 µm to achieve the reverse effect. The formation of gaseous species during the ablation with fs lasers will be shown. Various matrices and operating conditions, including sample humidity, laser energy density and spot size have been investigated and their influence on gaseous species formation will be reported.

References

[1] J. L. Todolí; J. M. Mermet Spectrochimica Acta Part B, 1998, 53, 1645-1656.

[2] D. A. Frick; D. Günther J. Anal. At. Spectrom., 2012, 27, 1294-1303.

[3] T. Van Helden; K. Mervič; I. Nemet; J. T. van Elteren; F. Vanhaecke; S. Rončević; M. Šala; T. Van Acker, Analytica Chimica Acta, 2024, 1287, 342089.

[4] F. Poitrasson; F.-X. d’Abzac J. Anal. At. Spectrom., 2017, 32, 1075-1091.