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根据单因素试验结果与响应面分析法中的Box-Behnken试验设计原理选取试验因素与水平,对葡萄有机酸提取率有影响的料液比、乙醇体积分数和pH值3个因素进行优化;结果表明:葡萄有机酸提取的最佳工艺参数为料液质量体积比1 g∶16 mL,乙醇体积分数76.37%,pH值11.87;在此条件下,葡萄有机酸质量分数为216.907μg/g。硫酸铜与柠檬酸、酒石酸和苹果酸反应生成的络合物吸收光谱重叠严重,用光度法难以进行单一组分的测定。采用偏最小二乘-光度法对柠檬酸、酒石酸和苹果酸模拟混合试样进行同时测定,并应用于葡萄有机酸的测定。对模拟混合试样,回收率99.6%~99.8%;RPEs为0.64%~0.67%。
According to the principle of Box-Behnken test in the single factor test and response surface analysis, the factors and levels of the test were selected, and the ratio of solid to liquid, ethanol volume fraction and pH were influenced by the extraction rate of organic acids. Results The results showed that the best technological parameters of organic acid extraction were the mass ratio of 1: 16: 1, the volume fraction of ethanol was 76.37% and the pH value was 11.87. Under this condition, the mass fraction of organic acids in grape was 216.907μg / g. The absorption spectra of the complex formed by the reaction of copper sulfate with citric acid, tartaric acid and malic acid overlap seriously, and it is difficult to measure the single component by photometry. Partial least square method - photometric method for citric acid, tartaric acid and malic acid mixed samples were simultaneously determined, and applied to the determination of organic acids in grapes. For the simulated mixed samples, the recoveries ranged from 99.6% to 99.8% and RPEs from 0.64% to 0.67%.