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Abstract

One of commonly used analytical technique for direct elemental analysis of solid samples is Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Although widely used for the analysis of various samples, obtaining accurate quantitative results remains a major challenge as matrix-matched standards are required. The aim of this thesis was to overcome these calibration issues by improving the quantitative capabilities of LA-ICP-MS through a comprehensive understanding of the factors affecting the processes and the introduction of a novel calibration approach based on ablated volume correction.
To understand the single pulse response (SPR) and the signal-to-noise ratio (S/N) of the measurement, it was essential to study the factors influencing the relationship between the stoichiometry of the sample and ablated and subsequently analyzed sample aerosol. We investigated the elemental fractionation during LA-ICP-MS analysis, focusing on the influence of fluence on the signal-to-noise ratio and the formation of double washout peaks. Systematic experiments and evaluation were used to gain deeper insight into these factors, allowing the development of strategies to mitigate their effects on the analysis results. An important contribution of this work was the introduction of a new calibration approach that eliminated the need for matrix-matched standards. By using 3D profilometry as a complementary tool, the morphology of the sample surface (e.g. ablated volume) was accurately determined after LA-ICP-MS analysis. This enabled the normalization of ICP-MS signals independent of matrix-matched standards or internal standardization methods and improved the accuracy and reliability of quantitative measurements.
The developed calibration approach was rigorously evaluated by bulk analysis and 2D mapping/imaging studies. All analytically relevant instrumental parameters were carefully optimized and the methods were partially validated and compared with existing techniques such as scanning electron microscopy. The results demonstrated the effectiveness of the new calibration approach in the accurate and precise quantification of elements in a wide range of sample types and matrices. Furthermore, the applicability of the developed calibration approach was demonstrated by the successful analysis of standard materials with different compositions. The thesis concludes with a discussion of the implications of these results for the wider field of elemental analysis and suggests avenues for future research to further develop LA-ICP-MS calibration methods.
Overall, this work represents an important step in overcoming calibration problematics in LA-ICP-MS analysis and sets the way for improved quantitative measurements in various scientific disciplines.