One-pot fabrication of magnetic porous Fe3C/MnO/graphitic carbon microspheres for dispersive solid-phase extraction of herbicides prior to their quantification by HPLC.

Magnetic porous microspheres composed of Fe3C, MnO and graphitic carbon (Fe3C/MnO/GC) were prepared by a one-pot method. A polycondensate obtained from urea and formaldehyde served as the carbon source and was calcined in the presence of metallic iron and manganese to yield Fe3C/MnO/GC. The resultant hybrid has highly mesoporous architecture, large specific surface, graphitic structure and adequate saturation magnetism. It is shown to possess excellent pre-concentration ability for herbicides (monuron, chlortoluron, atrazine and terbutylhylazine). The sorbent can be easily separated and has a long service lifetime (>25 cycles). Under optimized conditions, the sorbent excels by good recoveries (78-120%), high enrichment factors (45-50) and good precision (RSDs ≤10.7%). The limits of detection are 0.01-0.10 μg L-1 for (spiked) water samples, 0.22-0.87 μg kg-1 for grape samples, and 0.18-0.74 μg kg-1 for potato samples. This work offers a new strategy for the construction of magnetic bimetallic heterostructured GC hybrids. Graphical abstract Schematic presentation of magnetic porous Fe3C/MnO/graphitic carbon microspheres and their application for the enrichment of trace level herbicides prior to HPLC analysis.