Sensitive Detection Of Melamine Based On Surface Enhanced Raman Spectroscopy And Electrochemical Sensor Modified By Novel Nanomaterials

Melamine(C3N3(NH2)3)is a kind of three triazine heterocyclic organic compounds,because it has high nitrogen level(66 % nitrogen by mass),it has been illegally used for adulteration of milk products and various dairy products.Melamine is difficult to be metabolized and will result in renal failure and even death after being disgested by animal or humans.Therefore,it is necessary to develop a simple,rapid and highly sensitive technique for the detection of melamine in food.In this paper,three new methods for the sensitive detection of melamine have been developed.The main research is as follows:1.Determination of melamine by surface enhanced Raman spectroscopy based on the self-assembly ordered silver nanowires substrateA rapid and sensitive detection of trace amounts of melamine in sample was developed,in which a SERS substrate based on ordered silver nanowires(Ag NWs)was synthesized and assembled via polyol-fluid flow method.The characteristic Raman peak of melamine was obtained through the experimental investigation.And the detection conditions of melamine SERS on the substrate were optimized.Under the optimum conditions of water as solvent,p H=8,and solvent evaporation time of 14 min,a good linearity(R=0.997)between characteristic peak intensity and conce ntration of melamine was found in the range of 0.05 ?1.00 mg/L with the detection limit of 0.05 mg/L.The Recovery of melamine spiked in milk sample was from 89.7%~109.2% and the relative standard deviation was below 6.8%.2.Determination of melamine by surface enhanced Raman spectroscopy based on the graphene oxide supported gold nanoparticles substrateLoading the gold nanoparticles to the graphene oxide by redox reaction between HAu C l4 and graphene oxide,gold nanoparticles with diameter of about 70 nm was prepared by adjusting the mass ratio of chloroauric acid and graphene oxide.The detection conditions of melamine SERS on the substrate were optimized.Under the optimum conditions of p H=5,mixing intensity of 3 and sample amout of 60 ?L,a good linearity(R=0.993)between characteristic peak intensity and concentration of melamine were found in the range of 0.01 ?0.10 mg/L with the detection limit of 0.01 mg/L.The Recovery of melamine spiked in milk sample was from 89.0%~108.0%.3.Electrochemical determination of melamine on the glassy carbon electrode modified with MIL-101/Au NPs/CTS-PVP-RGOElectrochemical sensor based on MIL-101,Au NPs and CTS-PVP-RGO was prepared to detect melamine.The modified materials and electrodes were characterized and investigated by X-ray powder diffraction(XRD),scanning electron microscope(SEM),electrochemical impedance spectroscopy(EIS),cyclic voltammetry(C V)and differential pulse voltammetry(DPV).The sensor was used to detect melamine in milk samples under the optimal conditions of volume ratio of C TS and PVP-RGO of 2:1,50 s Au NPs adsorption time and 6 u L MIL-101 coating amount.The results indicated that the sensor exhibited a high sensitivity and good stability with the recovery between 92.0~104.0% and the linear range of 5.00×10-11~1.00×10-8 mol/L.The detection limit was as low as 5.00×10-11 mol/L.