Expanding the toolbox of rare earth quantification for bioaccumulation studies: Selective lanthanide determination using ICP-OES and sensitized luminescence for high throughput microbial screening
Year: 2026
Type: preprint
Abstract: Demand for rare earth elements (REEs) is expected to increase dramatically within the decade. Some REEs are deemed “critical” due to supply chain vulnerability and ubiquitous industrial use. As such, there is growing interest in biological separation of REEs from waste products such as coal ash, e-waste, and mine tailings. Accurately screening microbial candidates for metal sequestration is a crucial component of the viability of scalable REE reclamation. However, high throughput, selective metal quantitation within biological cultures remains a bottleneck for strain selection. Current methods for REE analysis include Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and the arsenazo III assay, the latter of which is indiscriminate for elements within the lanthanide series. Developing alternative methods for REE quantitation is critical for the scalability and potential automation of microbial screening. Hydroxypyridinone chelators, 5-LIO(Me-3,2-HOPO) and 3,4,3-LI(1,2-HOPO), were examined for their ability to act as spectroscopic antennas for Nd3+ and Eu3+ within microbial supernatant. Notably, 5-LIO(Me-3,2-HOPO) sensitizes the near-IR luminescence of Nd3+ for sub-μM quantitation. Nd3+ and Eu3+ luminescence assays exhibited strong calibration linearity (R2 = 0.9998 and R2 = 0.9997, respectively) with quantifiable concentrations as low as 0.137 µM for Nd3+ and 39 nM for Eu3+, outperforming arsenazo III for these elements. This work also demonstrates the effectiveness of Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) to quantify REEs for bioaccumulation experiments. ICP-OES quantitation limits for analytes (excluding Sm) were ≤33.1 ng mL-1 and ≤23.8 µg g-1 cell dry weight (CDW) for supernatant and biomass respectively. Matrix effects and spike recovery were also documented. Bioaccumulation experiments with Methylobacterium extorquens (AM1 and ΔmxaF) were used to compare ICP-OES and luminescence-based quantification, which showed percent differences of 7.7-8.2% for Nd3+ and ≤15.3% for Eu3+. Overall, sensitized lanthanide luminescence and ICP-OES offer reliable alternatives to existing analytical methods for REE determination.
Source: ChemRxiv
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7171540020