Analytical capabilities of LA-ICP-ToF-MS for ultra-fast 2D quantitative elemental mapping of micrometeorites
Chernonozhkin, S., Van Acker, T., Van Malderen, S. J., Belza, J., Goderis, S., & Vanhaecke
Journal of Analytical Atomic Spectrometry, 2024Â
DOI: 10.1080/02786826.2021.1874610
Stepan Chernonozhkin and his colleagues from Ghent University, Vrije Universiteit Brussel and Teledyne Photon Machines recently published their work on analyzing and quantifying the constituting elements of micrometeorites as well as reference materials using ultra-fast high-resolution 2D mapping. This work emphasizes the crucial role of the TOFWERK icpTOF 2R in conjunction with low-dispersion laser ablation (LA). This combination enables extremely rapid 2D mapping with micrometer-scale lateral resolution and a kHz laser pulse repetition frequency. Additionally, it records nearly the entire periodic table for every laser shot, ensuring comprehensive elemental mapping for each pixel of the image.
The ultra-fast 2D map generation by LA-ICP-TOFMS is significantly faster than traditional scanning-based LA-ICP-MS. It provides quantitative data by normalizing the sum of all element oxide levels to 100%, eliminating the need for a uniformly distributed internal standard. However, its application to geomaterials is rare, and the resulting element distribution maps are often considered semi-quantitative. The complexity of this approach arises from variations in mineral stoichiometry and fractionation behavior due to differing thermal interactions with the surface. Chernonozhkin and his colleagues showed that the LA-ICP-TOFMS should be the method choice for ultra-fast high-resolution 2D elemental mapping due to its ability of employing very small laser spot size with a mass range from Na to U at high laser repetition rates of 100-300 Hz. Each laser shot corresponds to a single pixel of the 2D map. Furthermore, the method is able to provide high-quality quantitative multi-elemental data of geological materials once the element contents are determined for each pixel. Mass fractions quantified showed no systematic bias and a very good precision for such an ultrafast multi-elemental mapping technique.
The maps of the micrometeorites obtained could complement and extend petrographic observations, and distinct chemical regions of interest could be recognized. Compared to traditional LA-ICP-MS, LA-ICP-TOFMS mapping allows determination of trace elements in complex microscopic zones without pre-identifying areas of interest or requiring an independent internal standard. It also monitors the full mass spectrum without needing pre-identification of nuclides. Additionally, it works with fast single pulse responses for higher sensitivity and throughput. LA-ICP-TOFMS is less destructive, which is also very beneficial for valuable or rare geological samples, such as these or other samples from asteroids, Moon, or Mars missions.
