Establishment Of Raman Assay Method Of Total Flavonoids In Vinegar Mud Of Shanxi Aged Vinegar

Shanxi aged vinegar has already become a famous business card of Shanxi Province and has special cultural significance for the Shanxi people.Therefore,it is necessary to protect the Shanxi aged vinegar brand.At present,the illegal behavior of aged vinegar on the market such as adulteration,year falsification,and even the use of glacial acetic acid to create counterfeit are endless,moreover,the consumption of vinegar is very dispersed,which makes it difficult to supervise the quality of the product against aged vinegar.For the front-line staff of market supervision,it is one of the difficulties to quickly identify the authenticity of Shanxi aged vinegar at the scene.It has practical significance to establish a fast and intelligent identification method for Shanxi vinegar.As the brewing of Shanxi aged vinegar has a unique geographical environment and a unique brewing process,the aged vinegar contains characteristic substances such as flavonoids and ligustrazine as characteristic indicators of Shanxi aged vinegar to judge its quality.In this experiment,a surface enhanced Raman spectroscopy method for the determination of total flavonoids in Shanxi Vinegar vinegar was established and compared with the conventional flavonoids detection method NaNO₂-Al?NO₃?₃-NaOH system colorimetry.Firstly,the common method of NaNO₂-Al?NO₃?₃-NaOH system colorimetry was used to evaluate the total flavonoids in aged vinegar mud.The results showed that the relative standard deviation of the method stability was5.31%and the relatively standard deviation of method reproducibility was2.98%,the relative standard deviation of method precision was 0.55%,and the average recovery rate of the method was 97.99%,indicating that this method was accurate and reliable in determining total flavonoids in vinegar mud;secondly,extracting the total flavonoids form the vinegar mud of Shanxi aged vinegar by ultrasonic-assisted ethanol extraction method and NaNO₂-Al?NO₃?₃-NaOH system colorimetry were used as the results determination method.The optimum extraction conditions were determined by response surface optimization based on the single factor experiment.The results showed that the best conditions of extraction processing are 60%of ethanol concentration,1:15 of solid-liquid ratio,50 min of ultrasonic time,50°C of ultrasonic temperature and 70W of ultrasonic power;finally,surface-enhanced Raman spectroscopy was used to detect crude extracts treated with calcium hydroxide and borax.The results of the detection were processed by an adaptive iterative reweighted penalty least square method to eliminate fluorescent background.Raman at 731 cm^-1 was selected as the characteristic peak and the Raman method is optimized and evaluated by this peak's height.The results showed that the best detection conditions of surface-enhanced Raman method are 5 times of integration times,25 s of integration time,and300 mW of laser power.The relative standard deviation of precision of Raman method was 7.82%,relative standard deviation of reproducibility was 4.33%,the relative standard deviation of the stability was 4.11%,the average recovery rate was 98.75%,indicating that the method is stable and reliable,can be used for the aged vinegar mud in the total flavonoid content detection.The experimental results show that the surface-enhanced Raman spectroscopy for the determination of total flavonoids in vinegar mud was poor compared to the NaNO₂-Al?NO₃?₃-NaOH system colorimetric method in precision and reproducibility,but the overall requirements for testing were met.Therefore,the Raman method is useful for the detection of total flavonoids in vinegar mud of Shanxi aged vinegar.