Rapid Detection Of Food Colorants Based On Surface-Enhanced Raman Spectroscopy At Trace Level

In order to make food with pleasing color,increase people's food habits and appetite,food additives were commonly used in food processing.Due to the lack of legal awareness and self-discipline awareness,some Chinese food production enterprises and small workshops abuse food additives for the benefit of the existence,result in endangering people's health seriously.To solve the phenomenon of food colorants,it is necessary for food production,processing,circulation and sales of all aspects of the implementation of full management and monitoring,of which fast and accurate detection of food additives is a necessary means.Traditional methods for the detection of food additives in food are spectrophotometry,chromatography,mass spectrometry and so on.These methods have the disadvantages of insufficient sensitivity and cumbersome measurement process.Therefore,it is very important to develop a fast qualitative and quantitative analysis model and a fast trace detection method which can carry out high throughput,high sensitivity and low detection limit.In this paper,a variety of common food additives were quantitatively modeled and tested on flower-shaped nano-silver substrates based on surface-enhanced Raman technology?SERS?.The main contents and results are as follows:1.The 3D-FDTD solutions simulation software was used to simulate the electromagnetic field enhanced distribution of single spherical and flower-shaped silver nanoparticle,double spherical and flower-shaped nano silver particles.The results obtained are as follows:1)The electromagnetic field excited by the silver nanoparticles is three times stronger than that of the smooth nano-silver sphere.2)In the double particles model,the electromagnetic field enhancement of the double particles is 10 times than that of the single particle model,and the electromagnetic field enhancement of the double flower model is still higher than that of the double sphere model.The SERS enhancement mechanism of flower-shaped nanostructures was studied in the direction of theoretical simulation.The orientated attachment?OA?theory of controlled growth of flower-shaped nano-silver was also explained from the experimental theory,which put forward the method of using PVP as a surfactant,and ASA as reductant to control the growth of flower-shaped silver nanoparticles.2.The silver nanoparticles were synthesized by liquid phase reduction method using silver nitrate?AgNO₃?as precursors,ascorbic acid?ASA?as reducing agent and polyvinylpyrrolidone?PVP-K30?as surface active agent.Based on the design of three orthogonal experiments,the flower-shaped nano-silver particles with different morphology can be prepared by controlling the reaction temperature,reaction time,reactant concentration and different reaction modes.Characterization of nano-silver particles by SEM can be used to find the shape of the flower-shaped and surface roughness of nano-silver substrate.Finally,the SERS substrate prepared by flower-shaped nano-silver particles was immersed in the probe molecule rhodamine6G?R6G?solution,dried and then subjected to SERS characterization.The optimal flower-silver particle preparation program:The best ratio of silver nitrate?AgNO₃?is0.2 mL of 1 mol/L,the best ratio of ascorbic acid?ASA?is 1 mL of 0.1 mol/L,and the best ratio of PVP-K30 is 2 mL of 1%wt.The SERS substrate with the size of the spherical silver nanoparticles is about 500⁸00 nm,the surface protrusions are about50⁷5 nm,and the samples are homogeneous.The EDS characterization and SERS characterization of the flower-shaped nano-silver substrate were optimized.The detection limit of R6G was 10^-9 mol/L.3.The surface enhanced Raman spectroscopy?SERS?technique was applied to the detection of food additives.The carmine detection was carried out on the flower-shaped nano-silver obtained by the orthogonal experiment in the previous chapter.First,by comparing the Raman spectral peak position and peak intensity information of the carmine solid powder and the carmine SERS spectral data based on nano-silver substrate,the peak values were identified and assigned through the literature,and the carmine Raman spectrum of multiple(10^-310^-8 mol/L)of the carmine samples were tested under the same experimental and test conditions and a detection limit of 10^-88 mol/L is obtained,which is lower than the detection limit of the existing national standard.The feasibility and advantages of SERS used in the detection of food additives are also proced.And then through applying SERS test in the four kinds of common food additives?bright blue,lemon yellow,sunset yellow,amaranth?based on flower-shaped nano-silver substrate,the wide applicability of the flower-shaped nano-silver substrate and SERS technology in food stains was further verified.4.In the last chapter,based on the SERS study of flower-shaped nano-silver substrate,a qualitative and quantitative analysis model of food additives was proposed.Based on the baseline,peak finding and principal component analysis?PCA?of SERS spectral data,the quantitative analysis model of the carmine was obtained by the algorithm.The results show that the goodness of the SERS characteristic peak information and the concentration curve is 0.9502,and by re-measuring the concentration of 5*10^-8 mol/L based on the flower-shaped nano-silver substrate of the carmine SERS data,the data back to the carmine qualitative quantitative analysis model to get the real concentration of information similar to the results,verify the accuracy of the model.