A Simple Method for Determination of Homologue Imidazolium Cations in Ionic Liquids Using IC with Direct Conductivity Detection

An investigation was carried out into the fast determination of five homologue imidazolium cations in ionic liquids by ion chromatography using a cation-exchange column and direct conductivity detection. Ethylenediamine, complex organic acid (citric acid, oxalic acid and tartaric acid) and organic modifiers (acetonitrile) were used as mobile phase. The influences of the eluent types, eluent concentration, eluent pH and column temperature on separation of the cations were discussed. Simultaneous separation and determination of the five homologue imidazolium cations in ionic liquids were achieved under an optimum condition. The optimized mobile phase was consisted of 0.25 mmol L(-1) ethylenediamine + 0.5 mmol L(-1) citric acid + 3% acetonitrile (v/v) (pH 4.1), set at a flow rate of 1.0 mL min(-1). The column temperature was 40 A degrees C and detection limits were obtained in the range of 1.1-45.6 mg L(-1). The relative standard deviations of the chromatographic peak areas for the cations were < 3.0% (n = 5). This method was successfully applied to separate imidazolium cations in ionic liquids produced by organic synthesis. The recoveries of spiked components were 92.5-101.9%.