| There are numbers of cis-diol-containing biomolecules exist in the biological body, such as nucleosides, glycoproteins/glycopeptide, neurotransmitters, saccharides and plant-based drugs. These compounds play significant roles in vital movement and clinical medicine, and often act as biomarkers of cancer, diabetes mellitus, neuroendocrine and cardiovascular disorders. Therefore, the analysis of the cis-diol biomolecules has attracted significant attention in many fields, i.e., metabonomics, proteomics research, and glycomics. However, the analysis of these compounds is confronted with great difficulties, due to their sub-stoichiometric nature along with their marked interference with biological matrices; therefore, sample pretreatment is highly desired prior to analysis.In this text, the magnetic solid phase extraction (MSPE) has the advantages of easy to operate, low consume of solvent and high extraction efficiency, these advantages were utilized to isolate and enrich low content of cis-diol compounds from the complex samples. The ferroferric oxide microspheres have the characteristics of good biocompatibility, large and easily chemically modified surface. Based on that, three kinds of boronate affinity magnetic adsorbents were designed around the selectivity and adsorption capacity performance. The aim of adsorption capacity enhancement was achieved by the increasing grafting number of the boric acid monomers on the surface of adsorbents. However, boronate affinity modification strategies have some drawbacks. So the zirconium-doped Fe3O4 adsorbent was designed to aviod these drawbacks, and the adsorption properties for cis-diol compounds were also investigated. The main research contents and results are in the following:1. The Fe3O4@SiO2 microspheres were acted as the support and activated by silane coupling agent, then the amination microspheres reacted with formylphenylboronic acid by "one pot" Schiff base reaction in the presence of NaBH3CN, so the single molecule boric acid group modified magnetic adsorbents Fe3O4@SiO2@FPBA were successfully synthesized. The microspheres showed high affinity and adsorption capacity to model substances. The maximum adsorption capacities for catechol and salbutamol were 96.0 and 50.0 μmol/g. It was successfully applied as boronic acid affinity MSPE and used for the determination of trace levels of SAL in pig tissue samples under the optimized conditions. The developed MSPE-HPLC method exhibited good parameters, and has a good linearity relationship in the range of 0.32-800 μg/kg. The limit of detection of SAL was reached to 0.19 μg/kg, and the recoveries were in the range from 89.5 to 107.9% under three spiked level with RSD less than 11.3%. Therefore, the developed method in this part can be applied for the detection of trace levels of SAL in complicated meat products.2. The polydopamine coated magnetic microspheres were prepared by a mild, sample and efficient method. A large number of active groups on the PDA surface were used to react with trithiocyanuric acid, and then two molecules of vinylbenzeneboronic acid were modified on the support by thiol-ene click chemistry reaction. The maximum adsorption capacity for dopamine reached to 409.3 μmol/g, this was due to the superposition of the adsorption abilities on Fe3O4@PDA and boronate affinity for cis-diol compounds. Because of the high hydrophily of PDA, the adsorbent could easily contact with target compounds to make the adsorption equilibrium achieved rapidly in 5 min. By using the adsorbent to determine the catecholamine neurotransmitter from urine, the developed MSPE-HPLC-FLD method exhibited excellent linearity relationship for three kinds of target compounds, and the recoveries were in the range of 89.3-109.2 ng/mL with RSD less than 11.6%, so the method has a low LOD, good reproducibility, and high precision. Therefore, the as-prepared adsorbent has the potential to selectively capture the cis-diol compounds in the complex samples.3. The presence of the amino groups on the surface of PDA coated magnetic microspheres was increased by hyperbranched reaction, and then the initiator groups were introduced to the material surface as much as possible. At last, the AAPBA monomers were modified on the microspheres by ATRP reaction, so the multilayer boric acid monomer brush has been successfully grafted to the Fe3O4@PDA@PEI@VPBA surface. In addition, we have found that the adsorption process could take place under pH 7.0, this can be attribute to the intermolecular B-N coordination between the molecules on the adsorbent surface. The maximum adsorption capacity for ovalbumin was 656.7 mg/g, it was 20-30 times higher than that for nonglycoprotein, and the adsorption equilibrium can be achieved in 30 min. Under the optimized conditions, the as-prepared adsorbent was used for the enrichment of OVA in egg white samples, it can be seen that the adsorbent has the value in practical application.4. We successfully synthesized novel Zr-doped Fe3O4 microspheres via a facile one-step hydrothermal method by adding reaction precursor in the mixture. Zr-doped Fe3O4 was shown to combine the selectivity of Zr and the characteristics of magnetic separation. The high affinity of the microspheres to cis-diol compounds was verified using a total of 27 compounds. In addition, the adsorbent had large adsorption capacities of up to 159.4 μmol/g for the nucleosides. By using the adsorbent to determine the nucleosides from urine, the developed MSPE-HPLC method exhibited excellent selectivity, a low LOD, good reproducibility, and high precision (LOD:0.005-0.017μg/mL, recoveries:77.8-119.6%, RSD<10.6%). To the best of our knowledge, this work is the first that explores the application of metal-doped Fe3O4 microspheres as an adsorbent for the separation of biological samples. The potential of the novel Zr-doped Fe3O4 microspheres to be used as a new type of adsorbent for the selective enrichment of cis-diol compounds from real biological samples have been proved in the experiment. |
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