A digital image-based method for determining of total acidity in red wines using acid-base titration without indicator.
A digital image-based method for determining of total acidity in red wines using acid-base titration without indicator.
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一种基于数字图像的方法，使用无指示剂的酸碱滴定法测定红酒中的总酸度。
DOI：
10.1016/j.talanta.2011.02.002
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发表时间：
2011
期刊：
影响因子：
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通讯作者：
E. N. Gaião
中科院分区：
文献类型：
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作者：
A. R. Tôrres;W. Lyra;Stéfani Iury Evangelista de Andrade;Renato A.N. Andrade;Edvan Cirino da Silva;M. C. U. Araújo;E. N. Gaião
本工作提出了使用基于数字图像的方法，通过酸碱滴定测定红葡萄酒中的总酸度，而不使用外部指示剂或任何样品的预处理。数字图像呈现出射辐射的颜色，这与葡萄酒中花青素所吸收的辐射是互补的。花青素会根据介质的pH值改变颜色，根据滴定过程中获得的图像中的颜色变化，可以准确和精确地定位终点。使用基于RGB的值来构建滴定曲线，并通过二阶导数曲线定位终点。官方方法建议使用NaOH标准溶液进行电位滴定，并将样品稀释至pH值达到8.2-8.4。为了说明该方法的可行性，对10种红葡萄酒进行了滴定。将结果与参考方法进行比较，通过在95%置信水平下应用配对t检验，未观察到结果之间存在统计学显著差异。所提出的方法比官方方法产生了更精确的结果。这是由于与数字图像相关的测量（RGB）的三变量性质。
This work proposes the use of digital image-based method for determination of total acidity in red wines by means of acid–base titration without using an external indicator or any pre-treatment of the sample. Digital images present the colour of the emergent radiation which is complementary to the radiation absorbed by anthocyanines present in wines. Anthocyanines change colour depending on the pH of the medium, and from the variation of colour in the images obtained during titration, the end point can be localized with accuracy and precision. RGB-based values were employed to build titration curves, and end points were localized by second derivative curves. The official method recommends potentiometric titration with a NaOH standard solution, and sample dilution until the pH reaches 8.2–8.4. In order to illustrate the feasibility of the proposed method, titrations of ten red wines were carried out. Results were compared with the reference method, and no statistically significant difference was observed between the results by applying the paired t-test at the 95% confidence level. The proposed method yielded more precise results than the official method. This is due to the trivariate nature of the measurements (RGB), associated with digital images.