Determining three isoflavones from Pueraria lobata using magnetic ZIF-8 nanoparticle-based solid-phase extraction and pressurized capillary electrochromatography

In this study, magnetic functionalized ZIF-8 nanoparticles were prepared by electrostatic self-assembly using magnetic Fe3O4 nanoparticles as cores and ZIF-8 as shells. ZIF-8 was used as the adsorbent to efficiently extract and sensitively analyze isoflavones due to its positive charge and strong adsorption capacity. Prepared samples were investigated by SEM and TEM, BET and ζ-potential analyses, FT-IR spectroscopy, powder XRD, and vibrating sample magnetism (VSM) experiments. The synthesized ZIF-8 has a dodecahedral structure that adsorbs well. Magnetic functionalized ZIF-8/Fe3O4 @SiO2 nanoparticles were prepared as a new SPE adsorbent, and a magnetic ZIF-8-pressurized capillary electrochromatography (pCEC) method was developed to separate and detect puerarin, daidzin, and daidzein (isoflavones) from Pueraria lobata by optimizing the extraction conditions, including adsorbent dosage, salt concentration, extraction time, desorption conditions, and other parameters. The developed method exhibited good linearities in the 50–2000 μg/mL concentration range for the three isoflavones, with coefficients of determination of 0.9934–0.9962. The limits of detection (LODs) for puerarin, daidzin, and daidzein were determined to be 0.02, 0.03, and 0.03 μg/mL, respectively. All analytes showed average recoveries in the 98.5–100.3% range, with relative standard deviations (RSDs, n = 6) of less than 4.0%. The developed method is convenient, enriches effectively, and shows good applications prospects for separating and analyzing components in Chinese herbal medicines.