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Voltammetric determination of the total acid content in ethanol-water mixtures. Application to distilled beverages

机译：伏安法测定乙醇-水混合物中的总酸含量。应用于蒸馏饮料

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The voltammetric behavior for the reduction of acetic and perchloric acid was studied with a platinum microdisk electrode in synthetic ethanol-water mixtures with an ethanol content of 40 and 50 vol.%. The results demonstrated that the reduction of acetic acid proceeds through a fast chemical reaction preceding the electrode transfer involving hydrogen evolution, as in water solutions, the dissociation constant of the acetic acid being greater than about 1 x 10(-6). This allowed us to derive an analytical expression relating the steady-state limiting current and analytical concentration of the weak acid. Depending on the concentration level, either standard addition procedures or an absolute equation proved valid to quantify the acid content of the synthetic: mixtures. The detection limits evaluated in the synthetic 40 and 50 vol.% ethanol-water mixtures, provided 1.92 x 10(-5) and 2.15 x 10(-5) M, respectively. The voltammetric procedure was applied to the determination of the total acid content in distilled beverages such as whisky, rum, vodka and grappa, having an ethanol content ranging from 38 to 50%. The results obtained with the proposed method were compared with the AOAC official method which requires a dilution of the sample in water, and a good agreement was found. Comparative measurements carried out directly in the real samples by acid-base titrations using either phenolpthalein dye or potentiometry with a glass electrode for end-point detection, gave unreliable results. [References: 28]
机译：用铂微盘电极在乙醇含量为40和50％（体积）的合成乙醇-水混合物中研究了还原乙酸和高氯酸的伏安行为。结果表明，在水溶液中，如在水溶液中，乙酸的还原是通过快速的化学反应进行的，该快速的化学反应涉及氢的逸出，乙酸的解离常数大于约1 x 10（-6）。这使我们能够推导有关稳态极限电流和弱酸的分析浓度的解析表达式。根据浓度水平，事实证明标准添加程序或绝对方程对量化合成混合物的酸含量均有效。在合成的40％和50％（体积）乙醇-水混合物中评估的检出限分别为1.92 x 10（-5）和2.15 x 10（-5）M。伏安法用于测定酒精含量为38％至50％的蒸馏饮料（如威士忌，朗姆酒，伏特加酒和格拉巴酒）中的总酸含量。将该方法获得的结果与AOAC官方方法进行了比较，AOAC官方方法要求将样品在水中稀释，并且发现了很好的一致性。使用苯酚酞染料或电位计通过玻璃电极进行终点检测，通过酸碱滴定直接在真实样品中进行的比较测量，结果不可靠。 [参考：28]

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