Search

The solubility of limonin in the binary solvent mixtures (methanol + water) and (acetone + water) with various initial mole fractions of methanol or acetone was measured by high-performance liquid chromatography (HPLC) at different temperatures ranging from 283.2 K to 318.2 K. The solubility of limonin increased with increasing initial mole fraction of methanol in (methanol + water) mixtures, whereas it had a maximum point at 0.9 mol fraction of acetone in (acetone + water) mixtures. The solubility of limonin increased with increasing temperature in the two binary solvent mixtures. The solubility of limonin was correlated with temperature by the van’t Hoff model and the modified Apelblat model, and the fitting results showed that the modified Apelblat model had better correlation. The CNIBS/Redlich–Kister model and the simplified CNIBS/Redlich–Kister model were used to correlate the solubility data with the initial solvent composition, the results show that the CNIBS/Redlich–Kister model reveals better agreement with the experimental values. Furthermore, to illustrate the effects of both temperature and initial solvent composition on the changes in the solubility of limonin, the solubility values were fitted by the Jouyban–Acree, van’t Hoff–Jouyban–Acree, modified Apelblat–Jouyban–Acree, Ma and Sun models. Among the five models, the Jouyban–Acree model give the best correlation results for (methanol + water) binary solvent mixtures, while the experimental solubility in the (acetone + water) system was most accurately correlated by the van’t Hoff–Jouyban–Acree model.

In this work, a superparamagnetic Fe 3 O 4 -graphene oxide (MGO) nanocomposite was prepared by one-step chemical co-precipitation method, and characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometer (VSM), powder X-ray diffraction (PXRD), Raman spectroscopy and nitrogen adsorption–desorption curve. The as-prepared MGO was used to adsorb nuciferine, and the adsorption kinetic, isotherm and reusability of MGO were also investigated. The results showed that the adsorption of nuciferine on MGO reached its equilibrium very quickly (within 10 min) due to the two-dimensional carbon nanostructure of GO. In comparison with MGO, five conventional sorbents, i.e., macroporous resin D-101, silica gel, reverse phase silica gel (RP-C18) and cation exchange resin and polyamide, were also used to evaluate their adsorption capabilities. Therefore, MGO combined the advantages of both superparamagnetic particle and GO, i.e., easy separation and high absorption capacity. Finally, MGO was successfully applied to enrichment and separation of nuciferine in the extract of Nelumbinis Folium (Lotus leaf).

In this work, the superparamagnetic Fe 3 O 4 particles prepared by the coprecipitation method were coated successively by SiO 2 , vinyl end groups and molecularly imprinted polymer (MIP) shells to afford a pomegranate-like core/shell superparamagnetic particle (Fe 3 O 4 @SiO 2 @MIP), and the MIP shell preparation conditions were optimized by multi-objective response surface methodology. In order to simultaneously enrich and separate the four taxoids (10-DAB, baccatin III, cephalomannine and paclitaxel), cephalomannine was selected as the template because of its similar chemical structure to other three taxoids and relative inexpensiveness. Especially, to avoid template leaking which may influence the accuracy of identification and quantitation of the analytes, we selected paclitaxel as the target molecular during the investigation of the adsorption property of Fe 3 O 4 @SiO 2 @MIP particles. This strategy was similar to the dummy molecular imprinting technique in which the dummy molecularly imprinted polymer was prepared by using a dummy template, structural analog of the target analyte. The as-prepared Fe 3 O 4 @SiO 2 @MIP particles were characterized by transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), and Fourier transform infrared spectroscopy (FTIR). The adsorption kinetics, isotherms and reusability were also investigated. Finally, the Fe 3 O 4 @SiO 2 @MIP particles were successfully applied to simultaneously enrich and separate these four taxoids in the extract of Taxus × media ( T. × media ).