Purification of imidazolium ionic liquids for spectroscopic applications

Abstract

Ionic liquids are often contaminated by colored impurities. These impurities can be problematic for spectroscopic studies or for monitoring organic reactions by UV/Vis spectroscopy. The effect of different purification methods on the optical quality of colored ionic liquids was studied and compared. Yellowish ionic liquids can partially be decolorized by treatment with active charcoal or by recrystallization. Our experiments show column liquid chromatography is not always a good technique to prepare spectrograde imidazolium halide ionic liquids. Colorless and UV-transparent ionic liquids were synthesized by a method that can exclude the need for further purification steps.

Composition and structural effects on the adsorption of ionic liquids onto activated carbon

“…Equilibrium adsorption measurements for 21 ILs were carried out with the aim of extending the number of compounds studied previously to a wide range of 48 ILs, which include a variety of anions (11) and cations (20), from imidazolium, pyridinium, ammonium, phosphonium, piperidinium and pyrrolidinium families. It permitted to analyse the effect of the different structural elements of an IL, such as the head group cation and anion substituents and nature, on the adsorption process.…”

“…[16][17][18] It is important to consider that in the framework of the development of sustainable processes, the ILs recycling aer regeneration or recovery must be envisaged. 8 Amongst the available non-destructive technologies, distillation, 19 crystallization, 20 nanoltration, 21 pervaporation, 22 separation treatment by using salts 23 and adsorption onto solids [24][25][26][27][28][29][30][31][32] are being increasingly studied. Adsorption onto activated carbons (ACs) has been recently demonstrated to be an effective and non-destructive technique for the removal of imidazolium-based ILs from aqueous solutions and their recovery for further use.…”

Ionic liquids in sample preparation

“…Due to its relatively short analysis time and simple procedure, this method could find wide application and universal utility in the analysis of various compounds [127]. The same ILs were also used to determine the enantiomeric purities of propranolol, naproxen, and warfarin by fluorescence spectroscopy [128].…”

Removal of Na+from Ionic Liquids by Zeolite for High Quality Electrolyte Manufacture

“…However, it has been revealed that those methods cause color changes or IL decomposition. [8][9][10][11] It appears that by established techniques, counter ions with same ionicity are unnecessarily removed, affecting the resulting ionic liquid's performance. A novel method to purify ILs without changing them is in great demand.…”