Dual-template magnetic molecularly imprinted polymer with minimal solvent consumption for simultaneous ultra-trace extraction of quercetin and kaempferol from medicinal plants using ultrasound-assisted dispersive solid-phase microextraction

This study reports the development of a dual-template magnetic molecularly imprinted polymer (MMIP) for the highly selective extraction of quercetin and kaempferol from complex matrices using ultrasound-assisted magnetic dispersive solid-phase microextraction (UA-MDSPME). The MMIP was synthesized via a multistep procedure involving the co-precipitation of Fe 3 O 4 nanoparticles, subsequent silica coating, amino functionalization, and dual-template molecular imprinting. Microscopic evaluation using field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) demonstrated clear differences in surface topology and internal architecture between the imprinted polymer (MMIP) and its non-imprinted analogue (MNIP), reflecting the successful generation of template-induced cavities within a heterogeneous core–shell framework. The progressive chemical modification of the material was validated by Fourier transform infrared (FTIR) spectroscopy, which confirmed the presence of characteristic functional groups introduced at each stage of synthesis. Vibrating sample magnetometry (VSM) revealed superparamagnetic behavior with sufficient saturation magnetization to enable rapid and efficient magnetic separation. A Plackett-Burman design (PBD) identified pH, MMIP mass, ultrasound irradiation time, and eluent volume as the most influential variables, which were further optimized using a central composite design (CCD) to maximize extraction efficiency. Under optimal conditions, the method demonstrated excellent analytical performance, including ultra-low detection limits (0.0103 ng mL − 1 for quercetin and 0.0018 ng mL − 1 for kaempferol), strong linearity (R 2 > 0.9929), satisfactory extraction recoveries ranging from 94.59% to 106.66% (RSD: 1.16–4.90%) for quercetin and 94.78% to 105.37% (RSD: 1.14–5.68%) for kaempferol, and high selectivity toward the target analytes. The imprinting factors (α) of 2.64 for quercetin and 2.61 for kaempferol further confirmed the enhanced molecular recognition capacity of the imprinted material compared with the non-imprinted control. The validated method was successfully applied to the analysis of six medicinal plant extracts, yielding recovery values of 94.78–106.66%, thereby confirming its robustness and practical applicability for the determination of flavonoids in complex plant matrices. Furthermore, the environmental sustainability of the proposed method was evaluated using the AGREE metric software, which assigned a favorable greenness score of 0.75. This score reflects the method’s compliance with the principles of green analytical chemistry, including minimal sample preparation, low reagent consumption, the absence of derivatization, reduced energy consumption through ultrasound-assisted extraction, and the reusability of the MMIP over multiple sorption–desorption cycles.