Sustainable and microwave-assisted extraction of tetracycline antibiotics from environmental water via magnetic pH-responsive block copolymer.

A pH-responsive magnetic nanocomposite (Fe3O4@SiO2@PGMA-b-PDEAEMA) was designed for organic solvent-free and rapid extraction of tetracyclines (TCs) from water samples via microwave-assisted magnetic solid-phase extraction (MSPE) coupled with high performance liquid chromatography (HPLC) analysis. The pH-modulated extraction was realized through changes in the conformation of PDEAEMA chains and ionization states of TCs for reversible adsorption without using organic solvents. Three representative TCs-oxytetracycline, tetracycline and doxycycline-were selected as the model compounds. The successful fabrication of the nanomaterial was confirmed by 1H nuclear magnetic resonance, transmission electronic microscopy, Fourier transform infrared spectroscopy, elemental analysis and vibrating sample magnetometry. The key parameters affecting the extraction efficiency were comprehensively investigated and the adsorption mechanism was carefully studied. Under the optimal conditions, the developed microwave-assisted MSPE-HPLC-UV method presented good analytical performance with short extraction time (90 s), limits of detection between 3.10 and 9.38 μg/L, relative recoveries ranging from 84.0 to 114 % and the relative standard deviations less than 9.4 %, confirming that this sustainable and rapid sample preparation method provided great potential for determination of TCs in environmental water. Lastly, the proposed method's greenness and practicality were evaluated using the Sample Preparation Metric of Sustainability and Blue Applicability Grade Index.