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The effect of polyethersulfone and nylon 6 micromembrane filters on the pyraclostrobin detection：Adsorption performance and mechanism
Summary
Researchers found that polyethersulfone and nylon 6 filtration membranes can adsorb up to 100% of pyraclostrobin fungicide from water samples, severely compromising the accuracy of environmental analyses that rely on filtration as a pretreatment step. The study characterised the adsorption kinetics and thermodynamics to help correct for or avoid this bias in pesticide monitoring.
Abstract Adsorption of test substances on micromembrane filters during sample pretreatment before qualitative and quantitative analysis has greatly affected the accuracy of the measurement. In the present study, it was found that the adsorption rate of pyraclostrobin reached 77.7-100% when water samples of pyraclostrobin (1 mL) were filtered with polyethersulfone (PES) and nylon 6 filters. Therefore, the adsorption mechanisms were investigated from the kinetics, isotherms, and thermodynamics of the pyraclostrobin adsorption process, combined with Attenuated Total Reflection-Fourier Transform Infra-Red (ATR-FTIR) spectroscopy and X-ray Photoelectron Spectroscopy (XPS) analysis. The adsorption of pyraclostrobin on the PES micromembrane is chemical adsorption; while Nylon 6 is physical adsorption. However, pyraclostrobin adsorption onto surface sites of Nylon 6 micromembrane was mostly through physical monolayer. The π-π electron-donor-acceptor (EDA) between pyraclostrobin and PES may promote the adsorption of PES to pyraclostrobin, and hydrogen bonding between pyraclostrobin and Nylon 6 micromembrane may be involved in the adsorption. Our study also proved the addition of methanol and iodine solution was an effective strategy to reduce the adsorption effects and to increase the accuracy of the detection.