紫外分光光度法测定功能性饮料中的咖啡因含量

Determination of Caffeine in Functional Beverages by Ultraviolet Spectrophotometry

采用紫外分光光度法测定四种市售功能性饮料中的咖啡因含量。根据所查阅的大量文献可知,乙酸乙酯提取咖啡因的最佳吸收波长为273nm,是测定功能性饮料中咖啡因含量的最佳条件。通过实验也摸索出了其他最适条件,最佳温度为30℃,最佳时间为15min。用标准溶液测吸光度,绘制出标准曲线,其咖啡因标液浓度与吸光度的线性回归方程为A=0.013 5c+0.011 7,相关线性系数R^2=0.995 8。4种样品分别在最适条件下处理后测定吸光度,得出四个样品中咖啡因含量分别为2.21%、5.43%、1.85%和10.11%。

This experiment uses ultraviolet spectrophotometry to determine the content of caffeine in four commercially available functional beverages.According to a large number of documents consulted,the optimal absorption wavelength of caffeine extracted by ethyl acetate is 273 nm,which is the best condition for determining the caffeine content in functional beverages.Through experiments,other optimal conditions have been found out.The optimal temperature is 30 ℃ and the optimal time is 15 min.The standard solution was used to measure the absorbance,and a standard curve was drawn.The linear regression equation of caffeine standard solution concentration and absorbance is A=0.013 5 c+0.011 7,and the correlation linear coefficient R^2=0.995 8.The four samples were processed under the optimal conditions The absorbance was measured,and the caffeine contents in the four samples were 2.21%,5.43%,1.85%,and 10.11%,respectively.