Study On Stripping And Identification Of Natural Dyes On Silk Fabrics

With the completion of a well-off society for all,the concept of ecological,healthy and green consumption began to take shape,and the market share of natural dye products gradually increased.However,the lack of relevant standards led to problems such as the protection of consumers' rights and interests and vicious competition among enterprises.Therefore,it is of great significance to study the identification methods of natural dyes on fabrics.In this paper,the stripping and identification methods of natural dyes on silk fabrics are studied.The color stripping of safflower yellow pigment,tea polyphenol and curcumin dyed fabric was studied by physical dissolution method.The effects of solvent,pH value,temperature,time,surfactant and complexing agent on the color stripping were discussed.The results show that surfactants and complexing agents have little effect on the color stripping effect.In the aqueous solution of 50%-70%acetic acid,the dyed fabric can be treated at 80-100? for 5-10 min to achieve a better color stripping effect.Safflower yellow pigment,tea polyphenol and curcumin dyed fabrics can be directly identified by acid-base color reaction,and stiped samples can be identified by aluminum trichloride ethanol solution fluorescence reaction and ferric trichloride aqueous solution precipitation reaction.The structures of the three pigments and their dyed fabrics were analyzed by UV,IR and Raman spectra.It is found that the maximum absorption wavelength of some decolorized samples of mordant dyed fabric is shifted,and the UV spectrum can be used as an auxiliary identification method.Compared with the infrared spectrum of the color standard and the peeled samples,it is found that the main structure of the peeled dye is not damaged,the vibration characteristic peak is basically the same,and the characteristic peak of some peeled samples is covered.The standard of safflower yellow pigment and curcumin is basically the same as the Raman spectrum of the dyed sample,and the Raman signal of tea polyphenol is weak,so it is not suitable for this detection method.It can be seen that Raman spectroscopy has some limitations.The best liquid chromatography conditions of safflower yellow pigment,tea polyphenol and curcumin were obtained.Redclassic C18 chromatographic column(250 m m*4.6 mm,5?m);flow rate 1000 ?L/min;injection volume 10 ?L;column temperature 30?;.The mobile phase of safflower yellow pigment was methanol acetonitrile 0.1%formic acid aqueous solution,the detection wavelength was 404 nm,gradient elution.The mobile phase a of tea polyphenols was 90 mL acetonitrile,20 mL acetic acid,2 mL EDTA-2Na solution(10 mg/mL),888 mL water.Mobile phase B was 800 mL acetonitrile,20 mL acetic acid,2 mL EDTA-2Na solution(10 mg/mL),178 mL water;detection wavelength was 278 nm;gradient elution.The mobile phase of turmeric pigment was methanol acetonitrile 1%acetic acid solution(23:48:52);the detection wavelength was 430 nm;isoelution.The RSD of the method was less than 3%.There was a linear positive correlation between the mass concentration of the main components and the peak area of the spectrum,and R2>0.99.In order to provide data support for the identification work,the quantitative analysis of fabrics with different dyeing process and different dye concentration was carried out.