Study On The Detection Of Chloramphenicol Drugs In Water Samples Based On Covalent Organic Framework Materials

Chloramphenicol drugs such as chloramphenicol,thiamphenicol and florfenicol have good inhibitory on a variety of bacteria.Therefore,they are widely used in aquaculture and animal husbandry to cure and control the occurrence of animal diseases.As a result,this kind of medicine will inevitably remain in the water of nature.Trace amount of drug residues not only increase the resistance of bacteria,but also accumulate in the human body after enrichment,causing great harm to the human body.However,in the case of the analysis and detection of chloramphenicol drugs in water samples,the interference of various substances may lead to a decrease in sensitivity of the method due to the complex composition of the water sample matrix.So the sample needs to be pretreated before the detection.Solid-phase extraction is a kind of pretreatment and quantitative detection method.This technique has several obvious advantages such as simple operation,high detection sensitivity and good recovery.Covalent organic frameworks?COFs?are a class of novel porous materials that are completely constructed from covalent bonds of small organic monomers.COFs have very unique properties,such as the regularity of the pore structure,the periodicity of the structure,low density,good stability and high specific surface area.As an important branch of porous materials,the development of synthetic routes and methodology and exploration of application fields of three dimensional?3D?COFs has been attracted special attention in the past decades.The first chapter of this thesis mainly introduces the synthesis,classification and application of COFs.Several common sample pretreatment methods especially solid phase extraction techniques in various fields were summarized and discussed.The second chapter focused on the preparation and characterization of 3D COF.An imine-based 3D COF was synthesized by solvothermal method.The structure was characterized by powder X-ray diffraction?PXRD?,fourier transform infrared spectroscopy?FT-IR?,scanning electron microscopy?SEM?,transmission electron microscopy?TEM?and BET nitrogen absorption analysis.FT-IR results indicated the formation of imine bond after the condensation reaction.PXRD data indicated good crystallization for the 3D COF.SEM and TEM results revealed that rod-like aggregations formed.BET nitrogen absorption characterization showed that 3D COF exhibited microporous structure with an average pore size of 1.03 nm.In the third chapter,we used the synthesized 3D COF as the sorbent in the solid phase extraction column to separate and enrich the chloramphenicol drugs in the water sample.The sample after the enrichment was tested by high performance liquid chromatography?HPLC?to conduct testing and analysis.First,five factors?eluent type,eluent volume,loading flow rate,pH and salinity of the water sample?affecting the extraction process were optimized.The experiment showed that the eluent was methanol/formic acid?97:3,V/V?;the eluent volume,15 mL;the loading flow rate,0.5 mL min^-1;the water sample pH,6;the salinity,15 under the conditions of the optimum adsorption.Methodological investigation of chloramphenicol was carried out under optimal conditions.The data showed that the detection limit of chloramphenicol was 0.01 ng/mL,and the detection limit of thiamphenicol and florfenicol was 0.03 ng/mL.The linear range of chloramphenicol was 0.1-200 ng/mL,and the linear range of thiamphenicol and florfenicol was 0.3-200 ng/mL.The R²value in the linear range is larger than 0.99.The recoveries were determined by the four concentrations of 0.5,10,100 and 150 ng/mL in the linear range.The recoveries ranged from 83.98%to 110.7%,indicating that the method can be applied to the determination of chloramphenicol,thiamphenicol and florfenicol in environmental water samples.