Ionic Liquids in Analytical Chemistry: Applications and Recent Trends

Abstract

Background: Ionic liquids (ILs) are a unique class of compounds consisting exclusively of cations and anions that possess distinctive properties such as low volatility, high thermal stability, miscibility with water and organic solvents, electrolytic conductivity and non-flammability. Ionic liquids have been defined as "design solvents", because it is possible to modify their physical and chemical properties by appropriately choosing cations and anions, in order to meet the specific characteristics based on their potential application. Introduction: Due of their tunable nature and properties, ILs are considered as the perfect candidates for numerous applications in analytical chemistry including sample preparation, stationary phases in liquid or gas chromatography, additives in capillary electrophoresis, or in mass spectrometry for spectral and electrochemical analysis. In the last years, the number of publications regarding ILs has rapidly increased, highlighting the broad applications of these compounds in various fields of analytical chemistry. Results: This review first described the main physico-chemical characteristics of ionic liquids, and subsequently reported the various applications in different subdisciplines of analytical chemistry, including the extraction procedure and separation techniques. Furthermore, in each paragraph the most recent applications of ionic liquids in the food, environmental, biological, etc. fields have been described. Conclusion: Overall, the topic discussed highlights the key role of ionic liquids in analytical chemistry, giving hints for their future applications in chemistry but also in biology and medicine.

Effects of Liquid Density on the Gas-Liquid Interaction of the Ionic Liquid Compressor for Hydrogen Storage

“…The hydrogen storage methods can be classified as compressed gas storage, cryogenic hydrogen storage, cryo-compressed hydrogen such as the density, viscosity, and surface tension, can be changed by adjusting the cation and anion constituents. Therefore, one of the famous features of the ionic liquid is its 'designability' as there are a huge number of ion combinations and the possibility of designing the target-pointing ionic liquid [38].…”

The Preparation of Novel Amino Acid Imidazole Ionic Liquids and Their Application as Stationary Phase for Capillary Gas Chromatographic Separations

“…[31] In 1959, Barber et al first reported the use of ILs as gas chromatographic stationary phases, [32] Since then, ILs-based gas chromatography stationary phases have been greatly developed. [33] In the early work, poor efficiencies, degraded analytes and poor peak shapes were obtained due to the fact that the molten salts had a limited temperature range between the time when they melted and the moment they decomposed. [34] In spite of such limitations, Armstrong et al detailed study and found that ILs have a major advantage for GC, namely their dual nature.…”

Extraction of Polyphenols from Olive Leaves Employing Deep Eutectic Solvents: The Application of Chemometrics to a Quantitative Study on Antioxidant Compounds

“…OLL phenols are mainly extracted using conventional solvents. However, recently, a move toward green methodologies under the name of green solvents, including ionic liquids (ILs) and deep eutectic solvents (DESs) or low-transition temperature mixtures (LTTMs), has emerged [16][17][18]. These new solvents aim at maximizing extraction efficiency and reaching new purposes such as researcher safety, environmental protection, and the use of a simplified and cheaper extraction procedure [19].…”