Advancing LIBS for Quantitative and Spatial Analysis of Rare Earth Elements in Coal

With the increasing global demand for rare earth elements (REEs), there is a critical need for rapid, field-deployable technologies that are capable of detecting and quantifying REEs in both conventional and unconventional resources. This work evaluates the use of Laser-Induced Breakdown Spectroscopy (LIBS) for the detection of lanthanum (La) and neodymium (Nd) in synthetic and natural rock and coal matrices at extraction-relevant concentrations. Multiple LIBS systems—including commercial and custom benchtop instruments (in single- and double-pulse modes), as well as a developing in situ LIBS probe—were employed. Detection limits as low as 10 ppm for La and 15 ppm for Nd were achieved, with double-pulse mode yielding signal enhancements of 3.5 to 6 times greater than single-pulse mode. Additionally, LIBS was compared with Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) across coal samples. Multivariate calibration and principal component analysis (PCA) enabled accurate classification and prediction of REE content, while 2D elemental mapping provided insights into the spatial distribution of REEs. The results demonstrate LIBS to be a promising tool for real-time REE analysis and resource assessment in both laboratory and field environments. LIBS is an emission spectroscopy-based analytical technique. A high-power laser pulse is used as an energy source to cause ablation of the test materials and achieve high-temperature plasma formation, which upon cooling emits light, giving characteristic information of the species that are present in the materials in terms of atomic and molecular spectra.