Preparation Of Open Tubular Capillary Column Modified With Graphene Oxide And Its Application

Objectives:We use the modified Hummers to prepared graphene oxide?GO?and grafting it on the capillary to preparate two kinds of open tubular capillary column by two different methods.We excepted to increase the phase ratio of stationary phase,improve the column capacity and achieve the higher separation efficiency of the solute via form two differentiated morphology thin layer in the inner surface of the capillary and expand the category of capillary electrophoresis analysis object.Besides that,we are also to provide an experimental basis in the preparation technology of open column,as well as the feasibility of this type column in actual sample application.Methods:1)The method to prepared GO and open tubular capillary:?1?Preparation of GO:The graphite powder as raw material,use the strong oxidation to preparate GO.?2?Preparation of OT_GO:The GO was grafted onto the capillary wall through the reaction between hydroxyl group of GO and epoxy group which modified in the inner wall by silanization reaction to form the graphene oxide modified open tubular capillary.?3?Preparation of OT_GO-MMAO-MMA which grafted by graphene oxide and methylmethacrylate copolymer:Dissolved the graphene oxide and methylmethacrylate in a solvent of DMF,under the action of the initiator,through radical polymerization with double bond in capillary inner wall which pretreatment by silanization reaction.Both of them graft copolymerization on the inner surface of the capillary to form graphite oxide and organic polymer copolymer thin layer of stationary phase.2)Characterization methods:?1?Characterization of GO:the infrared spectra of product;the test of solubility in different solvents;the observation of size and microstructure by atomic force microscope photograph.?2?Characterization of OT_GO:?a?The morphology of the capillary inner surface was observed by field emission scanning electron microscopy and compared to an uncoated capillary;?b?The electroosmotic flow?EOF?were tested in buffer at different pH and compared to an bared capillary.?c?The chromatographic behavior of the coated column was tested by separating four analytes with different polarity namely thiourea,phenol,cresol and bisphenol A,the RSD%of intra-day,inter-day and column to column were also tested.?3?Characterization of OT_GO-MMA:?a?The morphology of the capillary inner surface was observed by field emission scanning electron microscopy and compared to an bare column;?b?The electroosmotic flow?EOF?were tested in buffer at different pH and compared to an bare column.?c?The infrared spectra of graphene oxide and methylmethacrylate copolymer.?d?The chromatographic behavior of the coated column was tested by separating four neutral analytes namely thiourea,N,N-dimethylformamide,phenol and naphthol,the RSD%of intra-day,inter-day and column to column were also tested.3)Application:?1?Application of OT_GO:Six antidiabetic including metformin,phenformin,repaglinide,gliquidone,gliclazide and glipizide were analyzed,and their separation reproducibility were tested.?2?Application of OT_GO-MMA:To separated three nitrofurans:furazolidone,nitrofurazone,nitrofurantoin,and compared the separation efficiency to an bare column.Results:1.Preparation Results:The thickness of graphene oxide was uniformity and about 0.5nm measured by atomic force microscopy.The IR spectrum showed the carbonyl and hydroxyl were contained by graphene oxide.The prepared graphene oxide can be well dissolved in water,DMF,and cyclohexanol.2.Characterization results:?1?OT_GO:?a?The inner surface of the graphene oxide coated capillary column appeared hillocks and wrinkles while the bare column was smooth when they were observed by the field emission scanning electron microscopy.?b?The result of the electroosmotic flow?EOF?showed that the EOF of the coating column was significantly inhibited compared with the bare column.?c?The thiourea,phenol,cresol and bisphenol A can be separated completely by the coated column,and the stability was very good.The RSD%of intra-day,inter-day and column to column were 0.97%?6.24%and 20.43%,respectively.?2?OT_GO-MMA:?a?The inner surface of the graphene oxide and methylmethacrylate copolymer coated capillary column appeared wrinkles while the bare column was smooth when they were observed by the field emission scanning electron microscopy.?b?The result of the electroosmotic flow?EOF?showed that the EOF of the coating column was significantly inhibited and greater than OT_GO column by compared with the bare column.?c?The graphene oxide and methylmethacrylate were polymerized successfully by the test of IR spectrum.?d?The four neutral analytes can be completely separated by the column,and the stability was very good.The RSD%of intra-day,inter-day and column to column were 1.48%?5.83%and 8.50%,respectively.?3?Application Results:?a?The six antidiabetic including metformin,phenformin,repaglinide,gliquidone,gliclazide,glipizide could be separated completely under the condition of pH 4.0 in 50mmol/L citrate buffer,voltage 15 kV in OT_GO,the column efficiency were 196,910?197,267?116,836?21,596?92,375?72,254 plates/m respectively.RSD%of migration time were 0.54?0.12?1.02?1.05?1.21?1.40,and have a good reproducibility.?b?Three nitrofurans could be separated completely,under the condition of pH 11.0 in50 mmol/L phosphate buffer,voltage 15 kV in OT_GO-MMA and the column efficiency were 101,674?104,132?99,391 plates/m respectively.Conclusion:The graphene oxide was successfully prepared,then modified onto the inner wall of the capillary column in two ways.And then two kinds of opening column were successfully prepared that differ in microstructure.The phase ratio of stationary phase was increased,and the column showed chromatographic retention capacity especially for aromatic compounds.It also has a potential application for the real samples in separation and detection.This experiment provides a new way for extending the method and practical application in the new open tubular column.