Response Surface Methodology-Optimized Synthesis of ZIF-8 Nanoparticles and Its Application in the Extraction of Anthraquinones from Cassia Seed

In this study, response surface methodology (RSM) was employed to evaluate and optimize the key parameters for the solvothermal synthesis of Zeolitic Imidazolate Framework-8 (ZIF-8) nanoparticles, including solvent type, reaction temperature, reaction time, and material ratio. A multivariate regression model identified the optimal preparation conditions as ethanol as the solvent, a reaction temperature of 120 °C, a reaction time of 4 h, and a 5:1 molar ratio of 2-methylimidazole to zinc acetate. The resulting ZIF-8 nanoparticles exhibited highly selective adsorption capacity toward anthraquinones and were successfully applied to the rapid extraction and detection of five anthraquinones from Cassiae semen. By investigating the adsorbent dosage, adsorption efficiency, elution solvent, and elution efficiency, we established the optimal experimental conditions. Briefly, 20 mg of ZIF-8 nanoparticles were added to 10 mL of Cassia semen extract, and the mixture was shaken for 10 min before centrifugation. The residual anthraquinones in the supernatant were quantified by Ultra Performance Liquid Chromatography (UPLC). The adsorption efficiencies of aloe-emodin, rhein, emodin, chrysophanol, and physcion were 80.2%, 93.8%, 100%, 100%, and 100%, respectively. When eluted with methanol/100 mM NaHCO3 solution (1:1, v/v), the corresponding elution efficiencies of these compounds were 82.8%, 97.8%, 85.1%, 93.2%, and 65.3%, respectively. The relative standard deviations (RSDs) for method precision, stability, and repeatability were all below 4.0%. The prepared ZIF-8 nanoparticles showed favorable adsorption performance toward the five anthraquinone components. The method is simple to operate, requires minimal sample and solvent consumption, and can be used for rapid extraction and detection of anthraquinones in traditional Chinese medicinal materials such as Cassiae semen. This work provides a scientific reference for the application of MOFs nanomaterials in food safety inspection and quality control of traditional Chinese medicinal materials.