Departamento de Química Fundamental, Instituto de Química, University of São Paulo , São Paulo, Brazil.
Department of Chemistry, Clemson University , Clemson, South Carolina 29634, United States.
Anal Chem. 2017 Jan 17;89(2):1362-1368. doi: 10.1021/acs.analchem.6b04440. Epub 2017 Jan 3.
Concurrently with ethanol, many other compounds can be formed during the fermentation of grains and fruits. Among those, methanol is particularly important (because of its toxicity) and is typically formed at concentrations much lower than ethanol, presenting a particular challenge that demands the implementation of separation techniques. Aiming to provide an alternative to traditional chromatographic approaches, a hybrid electrophoresis device with electrochemical preprocessing and contactless conductivity detection (hybrid EC-CE-CD) is herein described. The device was applied to perform the electro-oxidation of primary alcohols, followed by the separation and detection of the respective carboxylates. According to the presented results, the optimum conditions were obtained when the sample was diluted with 2 mmol L HNO and then electro-oxidized by applying a potential of 1.4 V for 60 s. The oxidation products were then electrokinetically injected by applying a potential of 3 kV for 4 s and separated using a potential of 3 kV and a background running electrolyte (BGE) consisting of 10 mmol L N-cyclohexyl-2-aminoethanesulfonic acid (CHES) and 5 mmol L sodium hydroxide (NaOH). n-Propanol was used as an internal standard and the three carboxylate peaks were resolved with baseline separation within <3 min, defining linear calibration curves in the range of 0.10-5.0 mmol L. Limits of detection (LODs) of 20, 40, and 50 μmol L were obtained for ethanol, n-propanol, and methanol, respectively. To demonstrate the applicability of the proposed strategy, a laboratory-made sample (moonshine) was used. Aliquots collected along the beginning of the fractional distillation presented a decreasing methanol ratio (from 4% to <0.5%) and a growing ethanol ratio (from 80% to 100%) in the collected volume.
与乙醇同时，谷物和水果发酵过程中还会形成许多其他化合物。其中，甲醇尤为重要（因其毒性），且通常以远低于乙醇的浓度形成，这就提出了一个特殊的挑战，需要采用分离技术。本工作旨在为传统色谱方法提供替代方案，描述了一种带有电化学预处理和非接触式电导检测的混合电泳装置（hybrid EC-CE-CD）。该装置用于进行伯醇的电氧化，然后对相应的羧酸酯进行分离和检测。根据所呈现的结果，当样品用 2 mmol L HNO 稀释并施加 1.4 V 电位进行 60 s 电氧化时，可获得最佳条件。然后通过施加 3 kV 电位将氧化产物电注入，并使用 3 kV 电位和由 10 mmol L N-环己基-2-氨基乙磺酸（CHES）和 5 mmol L 氢氧化钠（NaOH）组成的背景电解质（BGE）进行分离。正丙醇用作内标，三个羧酸酯峰在 <3 min 内实现基线分离，在 0.10-5.0 mmol L 范围内定义线性校准曲线。对于乙醇、正丙醇和甲醇，检测限（LOD）分别为 20、40 和 50 μmol L。为了证明所提出策略的适用性，使用了实验室自制的样品（私酿烈酒）。在分馏开始时收集的等分试样中，甲醇的比例（从 4%降至 <0.5%）逐渐降低，而乙醇的比例（从 80%增加至 100%）逐渐增加。
