Magnetic Covalent Organic Framework for Efficient Solid-Phase Extraction of Uranium for on-Site Determination by Portable X-ray Fluorescence Spectrometry

Abstract

Uranium plays a pivotal role in the nuclear industry; however, its inadvertent release has raised concerns regarding health and environmental implications. It is crucial for a prompt warning and accurate tracing of uranium contamination in emergency scenarios. In this study, a novel and simple method was proposed that combines magnetic dispersive solid-phase extraction (MDSPE) with portable X-ray fluorescence spectrometry (XRF) for the on-site sampling and determination of trace uranium in real samples. A magnetic covalent organic framework (Fe 3 O 4 @COF) composite with excellent chemical stability and a large adsorption capacity of 311 mg/g was synthesized and employed as an efficient adsorbent for the solid-phase extraction of trace uranium. Without the need for a centrifuge or filter requirement, the established method by benchtop wavelength-dispersive Xray fluorescence spectrometry (WDXRF) exhibits an exceptionally low limit of detection (LOD) of 0.008 μg/L with a sample volume of 50 mL and a fast adsorption time of 15 min, rendering it suitable for environmental monitoring of UO 2 2+ . Consequently, this approach, in combination with a hand-held portable XRF instrument with an LOD of 0.1 μg/L, was successfully implemented for the on-site extraction and quality assessment of real water samples, yielding accurate results and satisfactory spike recoveries.

Field Detection of Uranyl in Coastal Water of China Using a Portable Device via DNA Photocleavage

“…An optical sensor, including fluorescence and colorimetry, is a prospective method that can be readily exploited for on-site analysis. − For instance, various approaches based on different materials (such as Au nanoparticles, AuNPs) as signal outputs have continuously emerged since Lu’s group innovatively reported uranyl-specific DNAzymes as catalytic beacon sensors with excellent sensitivity and selectivity toward uranyl. − However, the high salinity of seawater can severely affect the aggregation of AuNPs, and the high amount of K + can lead to false-positive results, resulting in the fact that most DNAzyme-based assays are still challenging in the analysis of uranyl in seawater. Wang and Qiu’s groups recently designed fluorescent metal–organic frameworks (MOF) and covalent organic frameworks with selective reaction sites to enable a specific analysis of uranyl in seawater. , Furthermore, Hou and Gong’s groups integrated the designed fluorescent MOFs with portable X-ray fluorescence spectrometry or drones to facilitate on-site sampling and detection of uranyl in the environment. , Besides, based on the unique uranyl-triggered photocleavage activity, the protein labeled with an aggregation-induced emission fluorescent molecule has been successfully used for ultrasensitive analysis of uranyl . However, the complex synthesis process of these nanomaterials and tagged biomolecules also results in multiple operations and high costs.…”