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Boronate-affinity magnetic hollow molecularly imprinted polymers (B-MhMIPs) were prepared with sialic acid (SA) as the template, 3-aminophenylboronic acid (APBA) as the functional monomer and glycidilmethacrylate (GMA) as the co-monomer to chemisorb Fe3O4 nanoparticles. Furthermore, the hollow structure made the nanoparticles have more binding sites at both internal and external surfaces, which can facilitate the removal of template molecules from polymers and enhance the adsorption abilities towards SA. After optimizing, the adsorption pH was controlled at 4.0, and this was different from most cis-diol-containing compounds. Under the optimal conditions, the limit of detection for SA was 0.025 μg mL−1 (n = 3). This method was applied to analyze serum samples with different spiked levels, and the recoveries of the SA were in the range of 70.9–106.2%. These results confirmed the superiority of the B-MhMIPs for selective and efficient enrichment of trace SA from complex matrices.

In this study, a new boronate-affinity hollow adsorbent was successfully fabricated. This adsorbent was prepared using mesoporous MCM-48 as a sacrificial support, methacrylic acid (MAA), N,N-methylenebisacrylamide (MBA) and azobisisobutyronitrile (AIBN) were applied as a functional monomer, cross-linker and initiator, respectively, and further modified with boronic acid groups (4-vinylphenylboronic acid, VPBA) to improve the enrichment efficiency. Such materials were composed of a hollow structure, a hydrophilic polymer coating of poly(MBA-MAA), and a VPBA-functionalized shell designed for capturing isoflavones. The resulting material coupled with high-performance liquid chromatography (HPLC) was applied to analyze three cis-diol isoflavones (daidzin, glycitin, and genistin) in soybean milk samples. The sorbent was characterized by transmission electron microscopy, Fourier transform infrared spectrometry and thermo-gravimetric analysis. Several parameters affecting the extraction efficiency were optimized. Owing to the hollow structure, more binding sites were located on the inner and outer surfaces of this material, which could facilitate the binding of the target molecules to the adsorbent. Adsorption selectivity studies indicated that the prepared material can selectively recognize isoflavones. Under optimized conditions, the limits of detection of the method were 3.8 to 7.3 μg L−1 for the three isoflavones based on a signal-to-noise ratio of 3 : 1. The spiked recoveries were found to be between 67.4 and 104.7% (the relative standard deviations were less than 3.8%, n = 3). This indicated the superiority of the method in selective extraction of isoflavones even from complex matrices.

Hollow structured l -lysine modified polydopamine coating shells (h-PDA@L-lys) were prepared using polystyrene (PS) as sacrificial support, the dopamine was used to coat PS by self-polymerization, L-lys as adsorpt ligand. The PS can be etched to form hollow structure, where more binding sites locate on the inner and outer surfaces can be utilized maximum. The h-PDA@L-lys were used as adsorbent for the specific bilirubin (BR) enrichment from animal livers. The adsorbent was characterized in details and its selectivity and binding capacity were evaluated. The experimental conditions (sample pH, adsorbent amounts, eluent types, eluent pH and volume) were optimized. The results indicate that h-PDA@L-lys exhibite good selective adsorption ability and higher adsorption amount. According to the adsorption experiments, the adsorption kinetics obey pseudo-second-order adsorption kinetics and the equilibrium data are best described by Langmuir isotherm model. The saturated adsorption capacity is 12.0 mg g−1, which is not only higher than the adsorption capacities of non-hollow adsorbents, but also superior to those of many reported adsorbents for enrich of BR. Moreover, this method was successfully applied in the selective recognition of BR in animal livers. Thus, this work provide potential possibility and practical platform for detection of BR in complex matrices.

D-Glucose was used as a dummy template in a strategy to fabricate boronate-based hollow molecularly imprinted polymers (h-MIPs) for the recognition of glycosides. 3-Aminophenylboronic acid (APBA) was selected as the functional monomer to impart glycoside binding capability. A polystyrene core was synthesized via an emulsifier-free emulsion polymerization. It was then be corroded to form a hollow structure where the binding sites on the inner surface can be fully utilized. Adsorption studies indicate that the resulting h-MIPs can specifically recognize glycosides. The h-MIPs were applied as a sorbent for solid phase extraction of the glycosides (daidzin, glycitin, rutin, and genistin) in soy products. Following desorption with 1% TFA in acetonitrile-water (3:7, v/v), the glycosides were quantified by HPLC with UV detection. The detection limits for the glycosides range from 3.5 to 10.8 ng·mL−1.

In this work, the boronate-affinity hollow stannic oxide based fragment template molecularly imprinted polymers (Bh@SnO2-FMIPs) were fabricated successfully. Polystyrene was used as sacrificial support, SnO2 was selected as inorganic matrix, surface imprinting using catechol as fragment template and 4-vinylphenylboronic acid as boronate-affinity functional monomer. A thin layer of poly 2-anilinoethanol (2-AE) was formed to coat the boronate-affinity hollow SnO2 surface through self-polymerization, it has strong hydrophilicity and limited residual boric acid content, avoiding non-specific binding. The hollow structure could bind to target molecules effectively and facilitate the removal of template molecules. The Bh@SnO2-FMIPs were used to extract three cis-diol polyphenols containing catechin, chlorogenic acid, and caffeic acid in tea and juice samples. Combination with seven characterizations of the material confirmed the successful preparation. Effecting the imprinting conditions and extraction efficiency parameters were optimized separately. Selective and competitive adsorption experiments indicated that the materials could specific recognition polyphenols. Using solid phase extraction and high performance liquid chromatography method, the detection limits were 0.005–0.046 μg mL−1 and the recoveries were between 82.3–104.3%. The improved adsorption performance may be assigned to the synergistic effects among boronate-affinity, hollow SnO2, and 2-AE self-polymerization. It may enhance binding cavities, hydrophilicity, biocompatibility of adsorbent material, and prevent the aggregation of Sn during the preparation processes.

γ-Al2O3 nanoparticle-bonded graphene oxide (γ-Al2O3-GO) was prepared for use as a solid phase extraction absorbent and for preconcentration of four nucleosides in human urine samples for investigation by high-performance liquid chromatography (HPLC). Transmission electron microscopy (TEM), thermal gravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FT-IR) were employed to characterize the absorbent. Several parameters (eluent species, absorbent amount, sample volume, and sample pH) were optimized, and the absorption efficiency was determined based on equilibrium absorbent amounts. Under optimal conditions, the γ-Al2O3-GO absorbent displayed enhanced absorbent ability for nucleosides. The calibration curve showed good linearities in the range of 0.10-10 mg/L for cytidine, inosine, and guanosine, and 0.05-10 mg/L for uridine; the correlation coefficient was observed to be in the range of 0.9967-0.9973. The limits of detection for the four nucleosides were in the range of 0.010-0.021 mg/L. Intra-day and inter-day relative standard deviations were 0.1%-0.8% and 1.0%-3.1%, respectively. The recoveries of the four nucleosides in urine samples ranged from 71.3% to 107.4%, and the relative standard deviations (n=3) were less than 4.8%. The results demonstrated that the proposed method is faster, more sensitive, and more efficient. Therefore, solid phase extraction (SPE)-based γ-Al2O3-GO can be considered more suitable for the determination and enrichment of nucleosides in urine samples.