Multi-elemental imaging using laser ablation and inductively coupled plasma mass spectrometry (LA-ICP-MS) for speleothems and tree rings

Author(s)

Danielle da Silva Francischini

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Química
• Defense date: 2023-08-18

Examining board members

Marco Aurelio Zezzi Arruda; Cassiana Carolina Montagner; Leandro Wang Hantao; Valderi Luiz Dressler; César Ricardo Teixeira Tarley

• Advisor: Marco Aurelio Zezzi Arruda

Abstract

This PhD Thesis is associated with the project "PIRE-CREATE: Climate research education in the Americas using tree-ring speleothem examples". In this sense, tree rings are considered growth layers produced by wood over a certain period of time, so they are considered biological records of changes in the environment. Speleothems are also pre-established matrices as archives of climate change, as they also incorporate trace elements into the calcium carbonate matrix according to the changes that have occurred at the site. Because they are matrices that have environmental information and micrometric regions, techniques that have high spatial resolution are of utmost importance to obtain satisfactory results. In this context, the imaging process emerges as an alternative that allows the analysis of the sample in its solid state, enabling access to information of chemical species spatial distributions and comparison with environmental information. The method known as laser ablation and inductively coupled plasma source mass spectrometry (LA-ICP-MS) has presented advantages in the imaging process due to the high spatial resolution, minimal sample preparation and high sensitivity, enabling qualitative and quantitative analysis of spatial information. In this context, this thesis had as general objectives the development of qualitative imaging methods of Zn, Ba, Mn, Fe, Ni, Sr, Ca and Mg for speleothems analysis (Chapter I), as well as quantitative imaging of Pb, Cd and Ba for tree rings by LA-ICP-MS technique (Chapter II). For both matrices, optimization of analytical parameters as well as imaging resolution of key elements was performed for the speleothem samples. For the method the quantitative imaging in growth rings by LA-ICP-MS, were evaluated to those based on calibration by matrix compatibility: (i) analytical curve and (ii) one-point, by using the species P. taeda as matrix of the analytical standards and three reference materials for analytical validation. As results of Chapter I, the positive influence of spot diameter and laser intensity on the isotope signal intensity was verified, as well as the influence of ablation speed and internal standard on the qualitative image resolution, making it possible to obtain high resolution images of the real speleothem sample surface. Regarding the results of Chapter II, linear correlation coefficients above 0.99 and analytical recovery between 74 and 110% were obtained for both quantification methods evaluated, which were applied in the quantitative imaging of Araucaria araucana sample, making it possible to quantitatively verify the heterogeneity of the growth rings. When comparing the quantitative imaging results with the results after decomposition and total quantification, it was also possible to verify that this heterogeneity of the matrix influences the validation of the results with conventional techniques, thus alerting to the search for new ways to validate quantitative imaging results beyond the total quantification via ICP-MS (AU)

• FAPESP's process: 19/00063-9 - Quantitative bioimaging of Cd and Pb through laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS imaging) to tree rings and speleothems
• Grantee: Danielle da Silva Francischini
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)