NiO/ZnO-Coated Carbon Microspheres for Dispersive Solid-Phase Extraction (DSPE) of Malachite Green and Crystal Violet in Aquatic Food Products with Determination by Ultra-High-Performance Liquid Chromatography (UPLC)

Developing highly efficient adsorbents toward trace pollutant analysis in complex biological samples is a challenge in analytical chemistry. Herein, NiO/ZnO-coated carbon microspheres (denoted by NiO/ZnO@C) with a well-defined core–shell structure were prepared through hydrothermal treatment and subsequent pyrolysis in air to enrich malachite green (MG) and crystal violet (CV). Hydrophilic carbon microspheres played an important role in the formation of core–shell NiO/ZnO@C, which may lead to the deposition of Ni2+/Zn2+ upon the surface via acidic chelating ligands. Based on the Langmuir model, NiO/ZnO@C demonstrated high adsorption capacities of 333.3 and 192.3 mg/g for MG and CV, respectively. Moreover, the NiO/ZnO@C composite served as a dispersive solid-phase extraction adsorbent to determine MG and CV in aquatic products combined with ultra-high performance liquid chromatography. High linearity was obtained for analyte concentrations from 5 to 500 μg/L with correlation coefficients (r) exceeding 0.9991. The limits of detection of the method were 0.50 μg/L (MG) and 0.35 μg/L (CV) with relative standard deviations less than 7.47%. Furthermore, the developed method was employed to determine MG and CV in aquatic products.