Rapid Determination of Pyrrolidinium Cations by Ion-Pair Chromatography With Imidazolium Ionic Liquids

This article describes a pioneering ion-pair chromatography with indirect ultraviolet detection with imidazolium ionic liquids (ILs) as ultraviolet absorption reagent and eluting agent for determination of pyrrolidinium cations. Three pyrrolidinium cations were analyzed on a reversed-phase silica-based monolithic column by isocratic elution with imidazolium ILs-ion-pair reagents-methanol mixtures. The effects of the ultraviolet absorption reagents, detection wavelength, ion-pair reagents, imidazolium ILs, organic solvents, column temperature and flow rate on the separation and determination of pyrrolidinium cations were investigated. Under the selected chromatographic conditions, the separation time was reduced to <2.5 min while maintaining excellent peak shapes and sufficient resolution. The detection limits for N-methyl-N-ethylpyrrolidinium cation, N-methyl-N-propylpyrrolidinium cation and N-methyl-N-butylpyrrolidinium cation were 0.12, 0.08 and 0.19 mg/L, respectively. Relative standard deviations for peak area were <0.59%. This simple and practical method has been successfully applied to the determination of three IL samples synthesized by the chemistry laboratory. The method is accurate, reliable and meets the requirements for quantitative analysis. In general, the analytical system and its associated methods appear to be widely applicable to determination of pyrrolidinium cations.