Determination of pyrrolidinium ionic liquid cations by ion chromatography-indirect ultraviolet detection with imidazolium ionic liquids as both an ultraviolet absorption reagent and an eluting agent

Abstract

An analytical method was developed for the determination of pyrrolidinium ionic liquid cations by ion chromatography with indirect ultraviolet detection using an imidazolium ionic liquid as both the ultraviolet absorption reagent and eluting agent. Chromatographic separation of pyrrolidinium cations was performed on a sulfonic acid base cation exchange column using imidazolium ionic liquid-organic solvent as the mobile phase. The effects of the background ultraviolet absorption reagents, imidazolium ionic liquids, detection wavelength, organic solvents and column temperature on the separation and determination of pyrrolidinium cations were investigated. The retention rules of the cations under different chromatographic conditions were discussed, and the chromatographic conditions were optimized. Under the optimal conditions, the detection limits (S/N = 3) for N-methyl-N-ethylpyrrolidinium cation ([MEPy]⁺), N-methyl-N-propylpyrrolidinium cation ([MPPy]⁺) and N-methyl-N-butylpyrrolidinium cation ([MBPy]⁺) were 0.34, 0.48 and 0.83 mg L⁻¹, respectively. Relative standard deviations (n = 5) for peak area and retention time were less than 1.1%. The method was applied in the determination of pyrrolidinium ionic liquids synthesized in a chemistry laboratory. Recoveries determined by the standard addition method were 94.0–98.7%. The method is accurate, reliable, and meets the requirements for quantitative analysis.