Detection Of Tryptophan And Quercetin By Molecularly Imprinted Sensor Based On Modified Multi-walled Carbon Nanotubes

The electrochemical sensor has attracted researchers′ attention due to its rapid response,low cost,high sensitivity,and simple sample handing.Molecularly imprinted polymers(MIPs),as a kind of materials with special recognition sites,have the characteristics of good stability,easy preparation,and environmental friendliness,and have been widely used in separation,solid phase extraction,sensor and other fields.Because of the poor conductivity of MIPs,they are often combined with nanomaterials with large surface area and strong catalytic ability,which can further improve the performance of the molecularly imprinted sensor,and realizing sensitive detection of complex samples.In this paper,electrochemical sensors with high specificity and sensitivity were prepared by combining molecularly imprinted polymer films with nanomaterials.The main work is as follows:1.Using tryptophan(Trp)as template molecule,methacrylic acid(MAA)as functional monomer,ethylene glycol dimethacrylate(EGDMA)as cross-linking agent,and2,2’’-azobis(2-methylpropionitrile)(AIBN)as initiator,molecularly imprinted polymers was synthesized on the surface of glassy carbon electrode(GCE)modified by ferrocene functionalized by multi-walled carbon nanotubes.And the molecularly imprinted sensor of tryptophan was prepared after elution.Scanning electron microscope,Fourier transform infrared spectroscopy and electrochemical techniques were used to characterize the surface morphology,electrochemical properties and sensing performance of the molecularly imprinted electrodes.The results show that the sensor can be reused and does not been disturbed by other substances during detection.Under the optimal conditions,the linear ranges are 1 μM-45 μM and 45 μM-330 μM,respectively,and the detection limit(S/N = 3)is 0.02 μM.It was used to determine the content of tryptophan in human serum and amino acid oral liquid,and the recoveries were 96.14%-104.54% and 95.65%-101.55%,respectively.2.Multi-walled carbon nanotubes were oxidized by the mixed acid,and then further combined with chitosan and immobilized on the surface of bare glassy carbon electrode.Then,using quercetin(Qu)as the template molecule,4-vinylpyridine(4-VP)as the functional monomer,EGDMA as the cross-linking agent,and AIBN as the initiator,molecularly imprinted polymer membranes was prepared on the modified electrode.The template molecule was removed by eluent,then the quercetin molecularly imprinted sensor was constructed.After a series of experiments,the molecularly imprinted composite electrode was characterized and the experimental conditions were optimized.The results show that the method has good repeatability and recognition ability to quercetin.Under the optimized experimental conditions,the sensor shows good analytical performance for quercetin in the concentration range of 53 μM-460.5 μM,with a detection limit(S/N = 3)of0.11 μM.The method was used to the detect quercetin in human serum,and the recoveries were 99.04%-103.85%.