Study On The Detections Of β-lactam Antibiotics In Environmental Water By Capillary Electrophoresis

Since the discovery of penicillin in 1928,antibiotics have been widely used in the prevention and treatment of various bacterial infections.β-lactam antibiotics are a class of antibiotics with aβ-lactam ring and different side chain structures.Due to its increasing consumption in clinical,animal husbandry and breeding industries,and the limitations of the wastewater treatment technology,β-lactam antibiotics have residues in various environmental medias.Capillary electrophoresis was established in the 1980s.It is an analytical technique to separate the analytes according to the difference in mobility of the analytes in the fused silica capillary.The separation of the analytes is driven by electroosmotic flow under the action of a high voltage electric field.The theoretical plate number of capillary electrophoresis can generally reach10⁵～10⁶/m,and its separation efficiency is extremely high.Micellar electrokinetic capillary chromatography is a separation mode of capillary electrophoresis.Micellar surfactant is used as the quasi-stationary phase.The analytes are separated under the multiple effects of electric field,electroosmotic flow and quasi-stationary phase,which broadens the range of analytes in capillary electrophoresis.Due to the low injection volume of capillary electrophoresis and the short optical path of the ultraviolet detector and diode array detector,the detection sensitivity of capillary electrophoresis is low.Enrichment of the analytes through the sample preparation technique is a method to increase the sensitivity of the analytical method.Currently,more and more new materials are applied to the sample pretreatment.The prepared materials generally can adsorb the analytes through various forces,and then the analytes can be separated from other impurities in the sample to achieve the purification and enrichment.Nanofiber membranes and magnetic materials are commonly used in sample pretreatment,which has the advantages of simple preparation,easy modification,large specific surface area,low cost,and environmental protection and safety.In this study,polypyrrole-modified nylon 6 nanofiber membranes and polypyrrole-modified magnetic nanoparticles were applied to the sample pretreatment,and then combined with the capillary electrophoresis for the detection ofβ-lactam antibiotics in the environmental water.Its main contents are:Part 1 Determination of twoβ-lactam antibiotics in river water by analysisObjective:Polypyrrole-modified nylon 6（PPy/PA6）nanofiber membrane was prepared.It was used in solid phase extraction and combined with the micellar electrokinetic capillary chromatography for the determination of oxacillin（OXA）and cloxacillin（CLOX）in the urban river.Method:PA6 nanofiber membrane was prepared by electrostatic spinning equipment.Under the oxidation of ferric chloride,the pyrrole monomer was polymerized into polypyrrole and modified on the PA6nanofiber membrane.Scanning electron microscope and Fourier transform infrared spectroscopy were used to characterize the prepared materials.In order to achieve efficient extraction and separation of OXA and CLOX,the separation conditions of capillary electrophoresis and sample preparation conditions were optimized.Under the optimal extraction and separation conditions,the water sample was filtered and then directly used for the determination.Results:Under the optimized sample pretreatment and separation conditions,the limit of detection（LOD）of OXA and CLOX was 2.0 ng/m L,and the linear relationship was in the range of 5.0～250.0 ng/m L.The linear correlation coefficient r>0.9968.The inter-day and intra-day precisions were2.38%～7.02%and 2.26%～5.29%,respectively.The spiked recovery was84.2～96.4%.Conclusion:PPy/PA6 nanofiber membrane dispersive solid phase extraction combined with the micellar electrokinetic capillary chromatography was established to detect OXA and CLOX in the urban river.The synthesis method and extraction process are simple.The method has high sensitivity,which provides new ideas for the determination ofβ-lactam antibiotics in the river water.Part 2 Magnetic dispersive solid phase extraction of fourβ-lactams based electrokinetic capillary chromatography analysisObjective:Polypyrrole-modified magnetic Fe₃O₄ nanoparticles（PPy/Fe₃O₄）were applied to the solid phase extraction and combined with the micellar electrokinetic capillary chromatography to determine OXA,CLOX,flucloxacillin（FLU）and dicloxacillin（DIC）in the urban river.Method:Fe₃O₄ nanoparticles were prepared by the chemical co-precipitation method.The pyrrole monomer was polymerized into polypyrrole and modified on Fe₃O₄ nanoparticles by the oxidation of ferric chloride.Fourier transform infrared spectroscopy and X-ray diffraction were used to characterize the materials.The separation conditions of capillary electrophoresis and the sample preparation conditions were optimized.Under the optimal extraction and separation conditions,the water sample was filtered and then directly used for the determination.Results:Under the optimized conditions,the LOD of OXA,CLOX and FLU was 1.0 ng/m L,and the LOD of DIC was 0.8 ng/m L.The linear relationship was in the range of 2.5～200.0 ng/m L.The linear correlation coefficient r>0.9988.The inter-day and intra-day precisions were2.95%～7.75%and 1.10%～7.66%,respectively.The spiked recovery was from 77.99%to 98.43%.Conclusion:PPy/Fe₃O₄ magnetic dispersion solid phase extraction combined with the micellar electrokinetic capillary chromatography was developed to determine OXA,CLOX,FLU and DIC in the urban river.The synthesis method is simple,and the extraction process is time-saving and simple.The established method has high sensitivity,which is suitable for the determination ofβ-lactam antibiotics in the river water.