Ionic Liquids in Chemical Analysis

Abstract

Room-temperature ionic liquids are salts with a melting point close to or below room temperature. They form liquids composed in the majority of ions. This gives these materials the potential to behave very differently when they are used as solvents compared to conventional molecular liquids. The search for their application is growing in every area of analytical chemistryelectrochemistry, chromatography, electrophoresis, and even mass spectrometry. The literature on ionic liquids is growing almost exponentially. The basis for this activity is the easy preparation of salts with different ion constituents. This ability might best be described as the "chemical tunability" of ionic liquids, a class of solvents with members possessing similar physical properties but having different chemical behavior. Their good solvating properties, together with large spectral transparency, make ionic liquids suitable solvents for spectroscopic measurements. It has been demonstrated that task-specific ionic liquids have advantages compared to common solvents used as separation media in liquid-liquid extraction processes achieving high efficiencies and selectivities of separation. The main advantage for other applications of ionic liquids in analytical chemistry lies in their low volatility which makes them useful as solvents for working in both high-temperature (gas chromatography (GC) stationary phases) and high-vacuum (MALDI matrixes) environments. When using an ionic liquid as an electrolyte medium, it is possible to achieve a broader range of operational temperatures and conditions relative to other conventional electrolytic media, and this makes ionic liquids promising materials in various electrochemical devices (e.g., batteries, fuel cells, sensors, and electrochromic windows).

Thermal Decomposition Behaviors of Imidazolium-type Ionic Liquids Studied by Pyrolysis-Gas Chromatography

“…1 In the field of analytical chemistry, ionic liquids are used as solvents for extraction and spectroscopic measurements, chromatographic stationary phases, matrix reagents for soft laser desorption/ionization mass spectrometry (MS), and electrolytes for electrochemical analysis and electrophoresis. [2][3][4][5][6] Due to not only their inherent ionic nature but also their high thermal stability and low volatility, the ionic liquids also have a potential as a specific media for sample preparation, especially for the thermal decomposition of polymeric materials and natural organic products. For this application, it is important to know the thermal decomposition behaviors of the ionic liquids themselves at elevated temperature.…”

Mutual Solubility of Hydrophobic Ionic Liquids and Water in Liquid-Liquid Two-phase Systems for Analytical Chemistry

“…More than a dozen review articles dealing with the application of ILs to analytical chemistry have appeared in the last five years. [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] Among many possibilities of applying ionic liquids, IL-water (W) two-phase systems that consist of an aqueous or a nonpolar molecular solvent and an ionic liquid are of considerable relevance with analytical chemistry and separation technology. A direct application of IL-W two-phase systems is the extraction of neutral compounds of relatively low molecular weights, [31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47] biopolymers 44,[48][49][50][51] and ions.…”

Electrochemical Aspects of Ionic-Liquid|Water Two-Phase Systems

“…R oom-temperature ionic liquids (ILs) that are salts in the liquid state have attracted much attention in a variety of areas because of their unique features, such as extremely low volatility, high polarity, and reasonable electrical conductivity (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11).…”