School of Chemistry, The University of New South Wales, Sydney, NSW 2052, Australia.
Anal Chem. 2012 Mar 20;84(6):2784-91. doi: 10.1021/ac2031173. Epub 2012 Feb 28.
An electrochemical method based on cathodic stripping voltammetry at a gold electrode has been developed for the determination of water in ionic liquids. The technique has been applied to two aprotic ionic liquids, (1-butyl-3-ethylimidazolium tetrafluoroborate and 1-butyl-3-methylimidazolium hexafluorophosphate), and two protic ionic liquids, (bis(2-hydroxyethyl)ammonium acetate and triethylammonium acetate). When water is present in an ionic liquid, electrooxidation of a gold electrode forms gold oxides. Thus, application of an anodic potential scan or holding the potential of the electrode at a very positive value leads to accumulation of an oxide film. On applying a cathodic potential scan, a sensitive stripping peak is produced as a result of the reduction of gold oxide back to gold. The magnitude of the peak current generated from the stripping process is a function of the water concentration in an ionic liquid. The method requires no addition of reagents and can be used for the sensitive and in situ determination of water present in small volumes of ionic liquids. Importantly, the method allows the determination of water in the carboxylic acid-based ionic liquids, such as acetate-based protic ionic liquids, where the widely used Karl Fischer titration method suffering from an esterification side reaction which generates water as a side product.
一种基于金电极阴极溶出伏安法的电化学方法已被开发用于测定离子液体中的水。该技术已应用于两种非质子离子液体（1-丁基-3-乙基咪唑四氟硼酸盐和 1-丁基-3-甲基咪唑六氟磷酸盐）和两种质子离子液体（双（2-羟乙基）铵乙酸盐和三乙铵乙酸盐）。当水存在于离子液体中时，金电极的电化学氧化会形成金氧化物。因此，施加阳极电势扫描或将电极电势保持在非常正的电位值会导致氧化物膜的积累。当施加阴极电势扫描时，由于金氧化物还原回金，会产生一个敏感的溶出峰。从溶出过程中产生的峰电流的大小是离子液体中含水量的函数。该方法不需要添加试剂，可用于原位测定小体积离子液体中存在的水。重要的是，该方法允许在广泛使用的卡尔费休滴定法因酯基化副反应而生成副产物水的羧酸基离子液体（如基于乙酸盐的质子离子液体）中测定水。
