Cu-MOFs/CMFP-EDXRF platform for sub-ppb level Pb detection in complex water matrices: Overcoming matrix interference via integrated enrichment.

BACKGROUND

With increasing heavy metal pollution, rapid on-site detection of trace lead (Pb) is urgently needed. Although energy-dispersive X-ray fluorescence (EDXRF) spectroscopy offers portability and multi-element analysis, direct water sample detection suffers from matrix scattering, making it difficult to achieve the WHO limit of 10 μg L-1.

METHODS AND

RESULTS

This study presents a novel integrated enrichment method using copper-based metal-organic framework modified carboxymethylated filter paper (Cu-MOFs/CMFP) for rapid EDXRF analysis of trace Pb in water. Pb2+ ions are enriched onto the solid Cu-MOFs/CMFP surface from aqueous samples, effectively reducing matrix interference and enhancing characteristic signals. Key parameters including pH, temperature, adsorption time, and instrument settings were optimized. Under optimal conditions (pH 4, 60 °C, 60 min adsorption, 7.5 W power, 300 s detection), the limit of detection reached 1.63 μg L-1. The high sensitivity derives from: (1) ion exchange and amino chelation between Cu-MOFs and Pb2+; (2) high surface area and active sites of CMFP; (3) internal standard calibration based on Compton scattering peak to correct matrix effects. The method exhibited strong anti-interference capability (coexisting ion signal deviation < ±5%), with good accuracy (recoveries 95.1%-104%) and precision (RSD <5%).

SIGNIFICANCE: This approach offers an efficient, practical solution for rapid on-site screening of trace heavy metals in complex environmental water samples.