Accurate Multi-element Content and Ratio Analysis of Stalagmites by Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry

Mg/Ca, Sr/Ca ratios and trace element contents in stalagmites provide important indices for high resolution paleoclimate reconstruction. In situ LA-ICP-MS analysis is introduced here instead of solution methods due to their large errors and mixing with multi-micro layers. The spatial distributions of Mg/Ca and Sr/Ca parallel to the growth axis of stalagmite are compared in sampling ways of line scan and spot ablation respectively, which consistently show significant cyclical variations. The line scan ablation with 40 μm beam spot has the advantages of high stability, high resolution, and of being fast and simple. The relationship of relative sensitivity coefficients and element fractionation are discussed among NIST 610, NIST 612, KL2G, ATHO-G and MASC-3. Indications are that the matrix effect is the main reason for the relative sensitivity coefficient change. The calibration method of 45 major, minor and trace elements in stalagmites was established by using normalization with multi-external standards and internal standard element of Ca. The matrix normalization of Ca and Mg major elements in forms of CaCO₃ and MgCO₃ with other elements, not only changes the calculation method of the content of the internal standard elements in domestic and foreign studies, when using other analytical techniques, but also avoids the problem of inaccurate detection of carbon successfully, which is consistent with the result when using internal standard element Ca.