RUI: Elucidation of Matrix Effects in Laser Ablation Elemental Analysis through Absolute Quantification of Ablated Mass

Arkansas State University Main Campus, Jonesboro AR

Investigators

Abstract

With support from the Chemical Measurement and Imaging Program in the Division of Chemistry, and co-funding from the Established Program to Stimulate Competitive Research (EPSCoR), Professor Jonathan Merten and his group at Arkansas State University are pursuing research that aims to make the measurement of the chemical elements around us easier, faster, cheaper and "greener." Elemental analysis is important to many fields, including geologic exploration, electronics, manufacturing, agriculture, energy, defense, and health. Typically, the measurement requires that the sample be dissolved in expensive and powerful acids before measurement, a process that can take hours and generates chemical waste with high costs for safe disposal. The Merten group seeks to improve understanding of alternative laser-based methods which are safer and much faster. Specifically, they direct pulsed lasers at samples to generate tiny plasmas hotter than the surface of the sun. Through better control and understanding of the plasma formation process, they are working to improve the laser-based measurements. Dr. Merten and his undergraduate students are also reaching out to the Northeast Arkansas community through programs at the Arkansas State Museum, which serves a rural population in Northeast Arkansas from its location on the campus of Arkansas State University. This work has the potential to provide >5000 participatory interactions with the public using free-form laser-ablation experiments performed in a class I, safety-interlocked laser setup at the museum, increasing public knowledge of and interest in spectroscopy and improving the STEM pipeline. Laser-ablation (LA) analytical methods, including laser-induced breakdown spectroscopy (LIBS) and LA inductively coupled plasma analyses require little or no sample preparation and are rapid and (in the case of LIBS) portable. Unfortunately, they are extremely prone to matrix effects, which are difficult to understand because of the inhomogeneous plasma?s small size and rapid evolution. The Merten group has developed a technique that allows mapping of the LA plasma with high spatial and temporal resolution. By spatially mapping the atomic absorption spectrum, it is possible to calculate the mass of the gaseous plasma. This "spectral massing" procedure is being used to improve understanding of the post-ablation plasma directly and dynamically, thereby enhancing understanding of the ablation process and its relationship to the signal in elemental analysis methods. Such understanding of the total atomized mass and its stoichiometric development is critical for LA analytical methods. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.