Green fabrication of fly ash-based magnetic adsorbent under water medium for the simultaneous capture of phenylurea and sulfonylurea herbicides prior to chromatographic quantification

Efficient extraction is an essential and challenging step in the simultaneous monitoring of the commonly used phenylureas (PUs) and sulfonylureas (SUs) in complex matrices. For this purpose, a new magnetic adsorbent based on fly ash (MAFA) was prepared through simple one-pot strategy without the application of organic solvent. The pre-treated fly ash, FeCl 3 and FeCl 2 were dissolved in water, and then the mixture reacted to form MAFA by means of simple one-pot hydrothermal technology for 2.5 h. The structure, morphology, spectroscopic, charged and magnetic properties were inspected by various characterized techniques. Combining the magnetic solid phase extraction (MSPE) format, the obtained MAFA presented satisfactory co-extraction performance towards PUs and SUs. The relevant adsorption process and behavior were well fit for Freundlich adsorption model and pseudo-second-order kinetics. After the optimization of extraction parameters, sensitive, reliable and practicable method for the simultaneous monitoring of studied PUs and SUs in aqueous and soil samples was developed by the combination of MAFA/MSPE and HPLC. The established method displayed high sensitivity (limits of detection were 0.0027–0.011 μg/L and 0.041–0.20 μg/kg for water and soil samples, respectively), good spiked recoveries (81.7–113 % and 81.0–114 % for water and soil samples, respectively) and excellent precision (RSDs did not higher than 9.2 %). Furthermore, approach accuracy was confirmed by means of confirmatory experiments.