Magnetic porous carbon material derived from imine-linked covalent organic frameworks for magnetic solid phase extraction of trace chlorine-containing herbicides in soil

Here, imine-linked covalent organic frameworks coated Fe3O4 microspheres were fabricated and employed as the self-template to prepare magnetic porous carbon material. The magnetic solid phase extraction (MSPE) perfor-mance of such magnetic covalent organic frameworks derived porous carbons (CMCOFs) were studied for the first time, and the improved MSPE performance was verified. The variations of chemical and material properties in the carbonization processes were studied, and it was found that the CMCOFs carbonated at 400 degrees C exhibited highest adsorption efficiencies for chlorine-containing herbicides due to the formation of nitrile components at this stage. The CMCOFs retained high adsorption efficiencies (above 90 %) to chlorine-containing herbicides at wide pH range (3-12) and high salt concentration. The CMCOFs-based MSPE coupled with HPLC technique was in good potential for analysis of trace chlorine-containing herbicides in soil samples. Under the optimized conditions, this approach displayed short extraction and elution time (5 and 8 min) and low limits of detection (0.35-5.5 ng/mL) for chlorine-containing herbicides. The recoveries of spiked analytes and the relative standard deviations in real soil samples were 81.86 %-110.9 % and less than 5.92 %, respectively. This study provides an efficient method for the analysis of trace chlorine-containing herbicides in complex samples, as well as give some inspiration on material modulation by controlled carbonization to achieve improved sorption performances.

Automated summary

Imine-linked covalent organic frameworks coated Fe3O4 microspheres were used as self-templates to prepare magnetic porous carbon material. The magnetic solid phase extraction performance of these magnetic covalent organic frameworks derived porous carbons (CMCOFs) was studied for the first time, and the improved extraction performance was confirmed. It was found that CMCOFs carbonated at 400 degrees C showed the highest adsorption efficiencies for chlorine-containing herbicides due to the formation of nitrile components. CMCOFs exhibited high adsorption efficiencies to chlorine-containing herbicides at a wide pH range and high salt concentration. CMCOFs-based MSPE coupled with HPLC technique showed potential for the analysis of trace chlorine-containing herbicides in soil samples, with short extraction and elution time and low limits of detection.