Use of corn straw-derived biochar for magnetic solid-phase microextraction of organophosphorus pesticides from environmental samples

In this study, the potentials of utilizing corn straw-derived biochar in environmental sample pretreatment were examined. An one-step magnetization and carbonization process was developed to prepare magnetic biochar by mixing corn straw powder with Fe2+/Fe3+ and then pyrolyzed at different temperatures (400-800 °C). The obtained magnetic biochars were characterized by using scanning electron microscopy, Brunauer-Emmett-Teller isotherms, X-ray diffraction and Fourier transform infrared spectroscopy. Various extraction affecting parameters, such as Fe2+/Fe3+content, pyrolytic temperature, species of desorption solvent, extraction and desorption time, respectively, were studied and optimized. Results showed that the magnetic biochar pyrolyzed at 700 °C exhibited the best extraction performance, with enrichment factors ranging from 52 to 210, presumably due to H-bonding and π-π interactions between biochar and organophosphorus, as well as to the high surface area and pore volume of biochar. The magnetic biochar-based extraction was further combined with gas chromatography-mass spectrometry (GC/MS) to analyze trace organophosphorus pesticides from environmental samples. The method demonstrated good linearity (0.1-50 µg·L-1), low limits of detection (0.02-0.11 µg·L-1), and high recoveries (72.4-96.8%) from spiked water and soil samples. The results of this study suggested the promising potentials of utilizing corn straw-derived biochar for efficiently enriching trace organophosphorus pesticides from complex environmental samples.