Imidozolium Ionic Liquids as Mobile Phase Additives in Reversed Phase Liquid Chromatography for the Analysis of Anions

Synthesis and applications of ionic liquids for chromatographic analysis

Ionic liquids (ILs) have emerged as more desirable liquids than conventional solvents for chemistry, material science, engineering and environmental science. The scientific literature reveals an exponential increase in the number of research projects aimed at exploring the chromatographic features of ionic liquids. The review provides sound scientific data to examine the structural characteristics of ionic liquids that make them ideal for use in chromatography. This contribution is distinctive since it integrates the synthesis, benefits, drawbacks, and possible uses of ionic liquids in several chromatographic separation processes. Keeping the cation the same, the introduction of different anions is also possible, and this strategy leads to the synthesis of a series of different ionic liquids with varying properties. A detailed probe is given on the influence of ionic liquid structure and properties on their chromatographic behavior, both as stationary phase and mobile phase and/or mobile phase additives. Ionic liquid based immobilized stationary phases and their analyte retention mechanisms (hydrogen bonding, electrostatic forces of attraction, π-π stacking, ion exchange, and hydrophilic interactions, etc.) are critically discussed. Finally, a thorough analysis of the literature suggests that IL-based stationary phases may undergo multi-mode and more flexible retention mechanisms. Their dual polarity can facilitate interaction with both polar and non-polar compounds. Similarly, using IL as a mobile phase can offer more pragmatic and sustainable options for enantiomer separation.

Separation and indirect ultraviolet detection of ferrous and trivalent iron ions by using ionic liquids in ion chromatography

A method of simultaneous separation and indirect ultraviolet detection of different valence iron ions Fe²⁺ and Fe³⁺ by using ionic liquids as mobile phase additives and ultraviolet absorption reagents on a cation exchange column functionalized with carboxylic acid group was developed. The effects of ionic liquids, organic acids, detection wavelength, etc. on separation and detection of Fe²⁺ and Fe³⁺ were investigated and the mechanism was discussed. The pyridinium and imidazolium ionic liquids were not only ultraviolet absorption reagents of indirect ultraviolet detection but also effective components for separating Fe²⁺ and Fe³⁺ . The separation and detection of Fe²⁺ and Fe³⁺ can be achieved using 0.5 mmol/L pyridinium ionic liquid-1.2 mmol/L methanesulfonic acid as the mobile phase. The determination of Fe²⁺ and Fe³⁺ had a good linear relationship in the concentration range of 1-100 mg/L. The limits of detection of Fe²⁺ and Fe³⁺ were 0.12 and 0.09 mg/L, respectively. This method was applied to the actual sample detection in the field of medical analysis. The spiked recoveries were between 97.3 and 99.5%, and the relative standard deviations were less than 0.6%. The method is simple, accurate, and reliable, and is an analytical method with universal and practical value.