Evaluating solid standards for LA-ICP-MS quantitative imaging of organisms with calcareous skeletons: accuracy, homogeneity, and laser wavelength effects

The literature provides examples of the use of different types of solid standards in the LA-ICP-MS analysis of organisms with calcareous skeletons. These include commercial glass standards, which chemically and physically differ from the carbonate matrix, and calcite-based laboratory-prepared pellets, whose homogeneity is often poorly documented. Furthermore, some works do not verify the accuracy of the results. Therefore, it is still unclear which calibration approach should be chosen when imaging calcareous specimens. In our work, the usefulness of various solid standards (NIST 610 and 612 glass standards, pellets produced by the addition of liquid elemental standards to calcite base and a standard made from powdered shells of Cerastoderma glaucum) was investigated in quantitative imaging of magnesium, strontium, and barium in coralline alga and bryozoan samples. Our study not only evaluated the impact of the standard's matrix on the accuracy of the results during the analysis of the in-house reference material but also examined whether the laser wavelength and internal standardisation could be crucial in obtaining reliable results. Additionally, for the first time, the homogeneity of the liquid-powder standards applied in previous works and the repeatability of their preparation method were thoroughly characterised.