Experimental and molecular docking study on graphene/Fe3O4 composites as a sorbent for magnetic solid-phase extraction of seven imidazole antifungals in environmental water samples prior to LC-MS/MS for enantiomeric analysis

In this work, a graphene modified by Fe3O4 nanoparticles (G-Fe3O4) was prepared and characterized. Seven chiral imidazole antifungals, including ketoconazole, econazole, miconazole, butoconazole, sertaconazole, fenticonazole and isoconazole were extracted from three environmental water samples by magnetic solid-phase extraction based on the G-Fe3O4, followed by enantiomeric analysis on a Chiralcel OJ-RH column coupled with a triple quadrupole mass spectrometry to evaluate their possible stereoselectivity during the degradation process occurring in the environment. Method detection and quantification limits for all the enantiomers were 0.11-0.32 ng/L and 0.28-0.67 ng/L, respectively. Satisfactory recovery (70-92%), good intra-day precision (RSD 3.1-12.0%) and inter-day precision (RSD 3.0-10.1%) were also obtained. Furthermore, the possible interactions between the analyte and graphene, such as electrostatic attraction, cation-pi interaction, hydrophobic interaction and pi-pi stacking were discussed by combining the experiment results and molecular docking study, which provided a new insight into the adsorption mechanism of analytes on graphene.