[Efficient separation of gossypol from cotton kernels with copper mediated magnetic molecularly imprinted polymer]

Cotton is an economically important crop in China. Cotton fibers are widely used in the textile industry and cottonseed is a key source of edible oils and proteins. Cottonseed contains gossypol （GOS）， a natural bioactive compound that exhibits medicinal properties， including antitumor and antiviral activities； it is also a potential contraceptive agent. Despite these benefits， GOS has some critical drawbacks， as it is associated with side effects such as antifertility and mammalian growth inhibition that limit the comprehensive utilization of cottonseed resources. Consequently， GOS needs to be efficiently and specifically separated for safe resource utilization. Conventional molecularly imprinted polymers （MIPs） have limitations as they often bind to targets in a manner that is too rigid or fragile， which leads to significantly lower specificities and mass-transfer rates. Accordingly， a novel copper-ion-mediated magnetic surface molecularly imprinted polymer （GOS/MIP） was designed and prepared to solve these problems. GOS/MIP integrates three key strategies： metal coordination， surface imprinting， and magnetic separation. Copper（Ⅱ） ions were introduced as functional "bridges" between the functional monomer and template， which resulted in softer and more flexible interactions and more homogeneous imprinted cavities. The imprinting sites were anchored to the surfaces of the functionalized magnetic cores， which accelerated the adsorption and desorption processes and simplified the preparation and separation steps. Free-radical polymerization enabled precise synthesis. GOS/MIP was thoroughly characterized， with scanning electron microscopy （SEM） and transmission electron microscopy （TEM） used to observe its morphology， and a vibrating sample magnetometer （VSM） used to measure magnetic properties. Energy-dispersive spectroscopy （EDS） was used to analyze the elemental composition， with Fourier-transform infrared （FT-IR） spectroscopy used to examine chemical bonding. The results confirmed the existence of a core-shell structure and that the imprinted layer had been successfully prepared. GOS/MIP was found to be composed of spherical particles 400-500 nm in diameter. The material also exhibited an excellent magnetic response， with a saturation magnetization of 47.78 emu/g， which enabled magnetic separation within only 7 s， thereby ensuring rapid recovery under practical conditions. Performance studies revealed that GOS/MIP exhibits an excellent binding ability for GOS， with equilibrium achieved in 120 min. The apparent maximum adsorption capacity and imprinting factor （IF） were determined to be 74.01 mg/g and 6.48， respectively. Selective and competitive binding experiments showed that GOS/MIP is highly specific for GOS in complex matrices， and pH binding experiments revealed that optimal binding occurs at pH 2-6， which covers most industrial processing conditions and highlights the large-scale industrial applications potential of the material. GOS/MIP retained its good adsorption capacity even after seven adsorption-desorption cycles， thereby demonstrating excellent stability and reproducibility. GOS/MIP was used as a dispersive solid-phase extraction （dSPE） adsorbent in combination with high-performance liquid chromatography （HPLC）. The developed method exhibited linearity in the 5-200 μg/mL range， with a high correlation coefficient （R²>0.999） and limits of detection and quantification （LOD and LOQ） of 0.024 and 0.079 µg/mL， respectively. Average recovery rates at three spiked concentrations （0.08， 0.24， and 0.80 μg/mL） ranged between 95.1% and 98.7%， with relative standard deviations （RSDs） below 2.4%. Only 50 mL of solvent and 50 mg of GOS/MIP were required in a simulated industrial GOS-separation process， which separated 3 mg of GOS from 10 g of cottonseed. GOS-recovery rates of 77.0%-83.3% were observed. The GOS/MIP-based separation method combines specificity， sustainability， and cost-effectiveness， thereby addressing the key challenges faced by traditional GOS-separation methods. In addition， it overcomes the toxicity limitations associated with the comprehensive utilization of cottonseed. Hence， cottonseed can be safely processed and cottonseed byproducts can be used in animal feed. This study provides a potent tool for the green， fast， and specific separation of high-purity products from plants； the basic research presented herein is both innovative and is potentially industrially applicable.