Related Experiment Video
Updated: Jun 26, 2026

In situ FTIR Spectroscopy as a Tool for Investigation of Gas/Solid Interaction: Water-Enhanced CO2 Adsorption in UiO-66 Metal-Organic Framework
Published on: February 1, 2020
Water as an in situ NMR indicator for impurity acids in ionic liquids
Yoshiro Yasaka1, Chihiro Wakai, Nobuyuki Matubayasi
1Institute for Chemical Research, Kyoto University, Kyoto 611-0011, Japan.
Abstract:
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.
Related Concept Videos
Chemical Shift: Internal References and Solvent Effects
The internal reference compound generally used in NMR spectroscopy is tetramethylsilane (TMS). TMS is preferred because it is chemically inert, soluble in NMR solvents, and easily removable. Also, the highly shielded methyl protons in TMS yield an intense...
Titration in Nonaqueous Solvents
Qualitative Analysis
For instance, group IV...
Leveling Effect and Non-Aqueous Acid-Base Solutions
The Leveling Effect of a Solvent
A generic acid (HA) reacts with the generic base (B-) to yield the corresponding conjugate base (A-) and conjugate acid (HB):
Indicators
Solubility of Ionic Compounds

