Metal-Organic Frameworks for the Trace Multiplexed Quantitation of 50 PFAS by Liquid Chromatography Mass Spectrometry

Per- and polyfluoroalkyl substances (PFAS) are environmental contaminants of increasing concern due to their persistence and potential health impacts. New guidelines with exceedingly low detection limits necessitate the development of promising materials for preconcentration. Six different metal-organic frameworks were evaluated for their potential as dispersive solid-phase extraction (dSPE) sorbents for PFAS quantitation by quantitative liquid chromatography tandem mass spectrometry (LC-MS/MS). UiO-66 demonstrated the highest combined average adsorption (87%) and recovery (85%) across 33 PFAS spiked in water at 2 ppb, and 75% recovery for 50 PFAS at 200 ppq. The developed dSPE workflow using UiO-66 resulted in limit of detections (LODs) as low as 4 ppq with average LODs of 108 ppq across 50 PFAS by testing at concentrations of 200 to 800 ppq. UiO-66 retained its crystalline structure post-PFAS adsorption, indicating stability for dSPE. Nearly 100% average recovery across all 50 PFAS was observed for UiO-66 using a 20 ppt spike, whereas ZIF-8 resulted in lower recovery. The efficacy of using UiO-66 as a dSPE material was assessed using six environmental water samples from different locations in Sydney, Australia, with all samples having quantifiable levels of PFAS. In water collected from Sydney Airport, 22 PFAS were detected above the limit of quantification (LOQ). Across all environmental water samples, a total of 25 PFAS were quantified above LOQs, with internal standard recoveries between 70-120%. In addition, the presence of multiply charged counterions decreased short-chained PFAS adsorption, while chloride had no impact. While polymeric resins have been used for screening ~50 PFAS with limits of detection ranging from 1 to 80 ppt, UiO-66 can be used to detect 50 PFAS at concentrations as low as 200 ppq. The high performance of UiO-66 in terms of recovery and detection limits underscores its potential for practical analytical applications in PFAS detection.