Water as an in Situ NMR Indicator for Impurity Acids in Ionic Liquids

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• 作者：Yoshiro Yasaka ; Chihiro Wakai ; Nobuyuki Matubayasi ; Masaru Nakahara
• 刊名：Analytical Chemistry
• 出版年：2009
• 出版时间：January 1, 2009
• 年：2009
• 卷：81
• 期：1
• 页码：400-407
• 全文大小：196K
• 年卷期：v.81,no.1(January 1, 2009)
• ISSN：1520-6882

文摘

A sensitive in situ NMR spectroscopic method for detecting acids contaminating ionic liquids (ILs) has been developed. The chemical shift and the spectral width of water added to ILs were used as indicators to measure the impurity acid level. Owing to the high resolution power of NMR, the detection limit is below the level of 10⁻³ mol kg⁻¹. A new method is applicable to a number of commonly used ILs such as the imidazolium- and ammonium-based ILs except for those composed of acidic cations or anions. The method was utilized to monitor the purification efficiency in the recrystallization of a typical hydrophilic IL, 1-butyl-3-methylimidazolium methanesulfonate from acetone. It was demonstrated that impurity acids can be almost perfectly removed by single or double recrystallization.