Bimetallic nitrogen-doped porous graphene for highly efficient magnetic solid phase extraction of 5-nitroimidazoles...

In this work, Fe/Ni bimetallic nitrogen-doped porous graphene (Fe/Ni-NPG) nanomaterials with rich pores, strong magnetism and good reusability were successfully prepared by one-step combustion and can be used as magnetic solid phase extraction (MSPE) adsorbents for the determination of 5-nitroimidazoles (5-NDZs) in environmental water samples. The dispersion and active sites of the materials were increased by the introduction of nitrogen. The adsorption behavior of Fe/Ni-NPG for 5-NDZs was investigated, which corresponds to the quasi-second-order kinetics and Langmuir adsorption model. The π-π electron donor-acceptor interaction (π-π EDA), hydrogen bond and electrostatic interaction between Fe/Ni-NPG and 5-NDZs are the main factors that help to obtain excellent adsorption properties. Several important conditions of MSPE are systematically optimized. Under the optimal MSPE conditions, the linear range of DMZ was 0.6-500 μg/L, the linear range of TNZ and ONZ was 0.7-500 μg/L, and the correlation coefficient R² ≥ 0.9991. The limit of detection was 0.18-0.2 μg/L, the limit of quantification was 0.6-0.7 μg/L, and the RSDs of intraday and interday precision were 1.58%-4.66% and 3.77-9.69%, respectively. In the three spiked actual environmental water samples, the recovery was 78.05%-107.05% (RSDs<7.82%). The results show that this method based on Fe/Ni-NPG provides an accurate and reliable way to detect 5-NDZs in environmental water.