| Microcystin-LR（Microcystin-LR,MC-LR）is an organic toxin produced by cyanobacterial cells with strong hepatotoxicity,nephrotoxicity,neurotoxicity and reproductive toxicity.To accurately quantify the content of MC-LR in the environment and remove MC-LR by a green and pollution-free manner has always been a research hotspot.Covalent organic frameworks（COFs）are highly crystalline porous materials,which are widely used in research fields due to their tunable structure and function,large specific surface area,well-ordered pores,and good biocompatibility.The first part of this paper was the development of Ultra High Performance Liquid Chromatography-Mass Spectrometry（UPLC-MS）and High Performance Liquid Chromatography-Variable Wavelength UV Detector（HPLC-VWD）methods for the determination of MC-LR.The sensitivity,precision and accuracy of the two methods were compared in detail.Quantification was performed using external standard method,and the linear ranges of UPLC-MS and HPLC-VWD were 0.08 to10μg/L and 1 to 5000μg/L,respectively.The detection limit and quantification limit of UPLC-MS were 0.03-0.05μg/L and 0.08μg/L,respectively,and the HPLC-VWD was 0.6 and 1.0μg/L,indicating that UPLC-MS method has higher sensitivity.Accuracy and precision experiments show that HPLC-VWD method has higher precision and accuracy.Statistical evaluation results showed that there was a significant difference between UPLC-MS and HPLC-VWD in the quantification of MC-LR at a concentration of 1μg/L.In addition,the potential adsorption effect of MC-LR on filters of different materials and pore sizes was also evaluated,and negative results were obtained.The UPLC-MS method is not affected by matrix effects.Finally,the developed UPLC-MS and HPLC-VWD methods were applied to analyze water samples from Erhai Lake in Dali,Yunnan.It was found that MC-LR was detected in water samples from Shuanglang Bay and Xi’er River,with concentrations of 0.120 and 0.120,respectively.0.303μg/L,while MC-LR was not detected by HPLC-VWD.In the second part,the Donor-Acceptor（D-A）type covalent organic framework（named NFP）was synthesized by solvothermal method,and the synthesis conditions were optimized.The degradation efficiency of MC-LR was taken as the guiding target,and the optimal synthesis temperature and optimal polymerization time were finally obtained.The synthesized NFP was characterized.The results of structure and morphology showed that the NFP was completely consistent with the theoretically designed structure,and its morphology was sea coral fibrous with high specific surface area（506 m~2/g）.The optical properties show that its band gap is 1.24 e V,and it exhibits light absorption in the range of 250～800 nm.It is also proved by fluorescence spectrum,photoluminescence spectrum,electrochemical and other characterizations that the triazine with electron withdrawing group is introduced,and the photogenerated carrier separation efficiency of NFP is significantly improved.The third part researched the degradation performance of MC-LR by simulating the photocatalytic reaction in the laboratory using the NFP synthesized in the second part as the photocatalyst.When the pH of the photocatalytic system solution was alkaline,the degradation efficiency was severely inhibited.However,there was no impact under neutral and acidic conditions.The as-synthesized NFP was compared with the classical inorganic semiconductor Ti O2,and the results showed that its degradation performance was 1.75 times higher than that of Ti O2.The catalyst can be repeatedly used even more than 5 times.The degradation mechanism of the system was studied by radical trapping experiments and electron spin resonance（ESR）experiments.In addition,the cytotoxicity of the degradation products of MC-LR was evaluated by the CCK8 method,and the results showed that the cytotoxicity decreased significantly with the increase of irradiation time.Finally,a mechanism for photocatalytic degradation of MC-LR with singlet oxygen as the main reactive oxygen species was proposed.In the fourth part,using doxorubicin hydrochloride as a model drug,NFP polymer drug-loaded nanoparticles were prepared by emulsification solvent evaporation method and solvent replacement method,respectively.The two methods were optimized,and finally the solvent replacement method was selected.The particle size of the drug-loaded nanoparticles prepared by the solvent replacement method was about 900 nm,and the stability was good.The drug loading rate and encapsulation rate were investigated.The maximum drug loading rate of the synthesized NFP was about 25%,and the drug loading amount of 5 mg of NFP was 1.25 mg.In addition,a quantitative method for doxorubicin hydrochloride by liquid chromatography was developed.The adsorption of doxorubicin hydrochloride by different materials of pinhole filters was investigated.Finally,a nylon filter membrane with a diameter of13 mm and a pore size of 0.45μm was selected to filter the doxorubicin hydrochloride solution.The results of stability experiments showed that the prepared drug-loaded nanoparticles had good stability,and the particle size did not change significantly in PBS solution for 48 h.Finally,the pH responsiveness of the drug-loaded nanoparticles was investigated.PBS buffer solution with pH 7.4 and acetic acid-ammonium acetate buffer solution with pH 4.5 were prepared respectively,and their in vitro release was simulated by dialysis.The results showed that in PBS buffer solution The total release of doxorubicin hydrochloride was 9.8%after 72 h,while the total release of doxorubicin hydrochloride in acetic acid-ammonium acetate buffer solution was as high as 70%,indicating that the drug-loaded nanoparticles had good pH responsiveness. |
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