Investigating The Rapid Detections Of Synthetic Pigment In Food By Combining TLC And SERS

Lemon yellow,sunset yellow and carmine are widely used in various kinds of food because of their advantages of easy color,low decoloration,low cost and so on.In recent years,it has been used by some illegal traders for the dyeing of tea and profiteering from it.However,the Ministry of health,"the standard for the use of food additives for food safety standards",has already clearly pointed out that the above substances are not allowed to be added in the tea.It is confirmed by experiments that if there is a large number of foods with excessive pigment content such as lemon yellow,sunset yellow and so on,people may suffer from allergies and diarrhea.When the intake is too large,it can cause a certain injury to the viscera.It may even affect children's intelligence,resulting in behavioral disorders such as hyperactivity.Therefore,it is of great significance to establish a simple,rapid and effective analytical method for the pigments,such as lemon yellow,sunset yellow and carmine,which are illegally added to foods.In this paper,TLC and SERS were used to detect lemon yellow,sunset yellow and carmine.Firstly,three different substrates were prepared by chemical reduction method,and characterized by UV-Vis absorption spectroscopy and transmission electron microscopy(TEM).The results show that the synthesized nanomaterials are spherical particles.Secondly,the thin layer chromatography plate and spreading agent were screened,and the parameters of the instrument and the conditions for the use of the enhanced substrate were optimized.The results show that the GF254 type chromatography plate is used for TLC experiment.The mixed solution,ethyl acetate,n-butanol,anhydrous ethanol,ammonia water and water(2:2:3:1:1,v/v/v/v/v),is used as the developing agent.High quality Raman spectra can be obtained by set as laser 785 nm,exposure time 10 s,and scanning times 10 times.The dropping amount of the substrate is 2?L,and it is added three times.It is determined that sodium chloride is used as the polymerization agent and the concentration is 10 mmol L-1.Thirdly,under the above optimum conditions,the minimum detectable values of three pigments were determined as follows:lemon yellow 2 mg L-1,sunset yellow 2 mg L-1,carmine 5 mg L-1.Based on the sensitivity and practicability of the method,four kinds of black tea samples were tested.In order to reduce the interference of external factors to the experimental results,the original spectral data and first derivative spectral data were processed and analyzed.PCA algorithm is used to identify three target objects.The results confirm that there are significant differences between the three target objects,which further confirms the practicability of TLC-SERS technology.