Zhang Li, Qi Hetong, Wang Yuexiang, Yang Lifen, Yu Ping, Mao Lanqun
Beijing National Laboratory for Molecular Sciences, Key Laboratory of Analytical Chemistry for Living Biosystems, Institute of Chemistry, the Chinese Academy of Sciences (CAS) , Beijing 100190, China.
Anal Chem. 2014 Aug 5;86(15):7280-5. doi: 10.1021/ac5014546. Epub 2014 Jul 18.
This study demonstrates a rapid visualization assay for on-spot sensing of alcohol content as well as for discriminating methanol-containing beverages with solvent stimuli-responsive supramolecular ionic material (SIM). The SIM is synthesized by ionic self-assembling of imidazolium-based dication C10(mim)2 and dianionic 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) in water and shows water stability, a solvent stimuli-responsive property, and adaptive encapsulation capability. The rationale for the visualization assay demonstrated here is based on the combined utilization of the unique properties of SIM, including its water stability, ethanol stimuli-responsive feature, and adaptive encapsulation capability toward optically active rhodamine 6G (Rh6G); the addition of ethanol into a stable aqueous dispersion of Rh6G-encapsulated SIM (Rh6G-SIM) destructs the Rh6G-SIM structure, resulting in the release of Rh6G from SIM into the solvent. Alcohol content can thus be visualized with the naked eyes through the color change of the dispersion caused by the addition of ethanol. Alcohol content can also be quantified by measuring the fluorescence line of Rh6G released from Rh6G-SIM on a thin-layer chromatography (TLC) plate in response to alcoholic beverages. By fixing the diffusion distance of the mobile phase, the fluorescence line of Rh6G shows a linear relationship with alcohol content (vol %) within a concentration range from 15% to 40%. We utilized this visualization assay for on-spot visualizing of the alcohol contents of three Chinese commercial spirits and discriminating methanol-containing counterfeit beverages. We found that addition of a trace amount of methanol leads to a large increase of the length of Rh6G on TLC plates, which provides a method to identify methanol adulterated beverages with labeled ethanol content. This study provides a simple yet effective assay for alcohol content sensing and methanol differentiation.
本研究展示了一种快速可视化检测方法，用于现场检测酒精含量以及鉴别含甲醇饮料，该方法采用了对溶剂刺激响应的超分子离子材料（SIM）。SIM通过基于咪唑鎓的双阳离子C10(mim)2与双阴离子2,2'-偶氮双（3-乙基苯并噻唑啉-6-磺酸）（ABTS）在水中进行离子自组装合成，具有水稳定性、溶剂刺激响应特性和自适应包封能力。此处展示的可视化检测原理基于SIM独特性能的综合利用，包括其水稳定性、乙醇刺激响应特性以及对光学活性罗丹明6G（Rh6G）的自适应包封能力；向Rh6G包封的SIM（Rh6G-SIM）的稳定水分散体中加入乙醇会破坏Rh6G-SIM结构，导致Rh6G从SIM释放到溶剂中。因此，通过加入乙醇引起的分散体颜色变化，可直接用肉眼观察酒精含量。酒精含量也可通过测量Rh6G-SIM释放到薄层色谱（TLC）板上的Rh6G荧光线来定量，以响应酒精饮料。通过固定流动相的扩散距离，Rh6G的荧光线在15%至40%的浓度范围内与酒精含量（体积%）呈线性关系。我们利用这种可视化检测方法现场可视化三种中国商业烈酒的酒精含量，并鉴别含甲醇的假冒饮料。我们发现加入微量甲醇会导致TLC板上Rh6G的长度大幅增加，这提供了一种识别标注乙醇含量但掺有甲醇的饮料的方法。本研究提供了一种简单而有效的酒精含量检测和甲醇鉴别方法。
