Overcoming matrix effects in EDXRF: a dual N, S-coordinated cellulose platform for ultrasensitive and selective mercury monitoring in complex aquatic matrices.
Abstract
BACKGROUND: Mercury (Hg) contamination in aquatic environments presents a critical threat to ecological stability and human health due to its extreme toxicity, environmental persistence, and bioaccumulation potential. While trace Hg detection is essential for environmental safety, conventional analytical methods are often hindered by the requirement for expensive laboratory-grade instrumentation, labor-intensive sample preparation, and limited field utility. Bridging the gap between high-performance analytical requirements and the need for portable, rapid monitoring is paramount. Consequently, there is an urgent need to develop a cost-effective and field-deployable strategy that enables high-sensitivity detection of trace Hg in complex environmental water matrices. RESULTS: We developed a novel analytical strategy integrating energy-dispersive X-ray fluorescence (EDXRF) spectroscopy with a thiosemicarbazide-functionalized cellulose-based substrate (TSC-CMFP). By grafting N,S-rich ligands onto carboxymethylated filter paper, we achieved selective Hg2+ capture through soft Lewis acid-base coordination. Under optimized conditions (pH 3.0, 70°C adsorption, 30 min duration), the method attained a low detection limit of 1.37 μg L-1. The use of Rayleigh scattering as an internal standard effectively minimized matrix interference. Experimental validation confirmed high selectivity against coexisting ions, robust reproducibility (RSD < 4%), and excellent storage stability for up to seven days. Furthermore, the method exhibited high accuracy in real water sample analysis, with spiked recoveries of 96.47-102.25%, demonstrating strong agreement with ICP-MS benchmarks. SIGNIFICANCE AND NOVELTY: This work introduces a synergistic platform that fuses the inherent portability of EDXRF with highly specific N,S-chelation chemistry. By transforming liquid-phase mercury into a stable solid-state signal, this approach overcomes the sensitivity limitations of portable X-ray systems. It provides a practical, high-throughput, and field-ready solution for environmental monitoring, offering a transformative tool for rapid mercury screening in complex, resource-limited, or remote field settings.
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