Determination Of Imidazolium Ionic Liquid Cations By Ion Chromatography

An investigation into analysis of imidazolium ionic liquid cations by ion chromatography was carried out. The purpose of this research is to develop accurate, fast and simple methods to determine ionic liquid cations by ion chromatography.Firstly, an investigation into the determination of four imidazolium ionic liquid cations by ion chromatography using a carboxyl acid cation-exchange column and direct conductivity detection was carried out. Using inorganic acid (sulfuric acid) or organic acid (citric acid and oxalic acid) + acetonitrile as eluent, the effects of the types of eluent, eluent concentration and column temperature on retention times of the cations were investigated. This research has developed a simple, accurate ion chromatography method for separation and determination of imidazolium ionic liquid cations. The method has been successfully applied to the determination of two ionic liquids synthesized by organic chemistry lab. Recoveries of the cations after spiking were 98.5 %– 102.1 %. And the study results are helpful for improving practical value of determination of ionic liquid cations.Secondly, the determination of five imidazolium ionic liquid cations by ion-pair chromatography was carried out using ultraviolet detection. Chromatographic separations were performed on a ZORBAX Eclipse XDB-C18 column. The effects of ion-pair reagents, acetonitrile concentration and column temperature on retention of the cations were investigated, and simultaneous separation of five imidazolium cations was achieved under the optimum conditions. Detection limits for the cations were 0.05– 0.30 mg/L. Relative standard deviations (n = 5) for peak areas were less than 0.1 %. The method has been successfully applied to the determination of two ionic liquids synthesized by chemistry laboratory. Recoveries of the cations after spiking were 98.6 %–102.1 %. Using gradient elution procedure, the analysis time was short, and detection limits were low.Thirdly, the determination of imidazolium ionic liquid cations by ion chromatography using a monolithic column and direct conductivity detection was studied. Experiments were performed on a Chromolith Speed ROD RP-18e column (100 mm×4.6 mm i.d.) with 1-heptanesulfonic acid sodium + acetonitrile + citric acid as eluent. The effects of eluent concentration, eluent pH, column temperature and flow rate on retention time of the cations were investigated. Simultaneous separation of four imidazolium ionic liquid cations was achieved under the optimum conditions. Detection limit for the cations was 1.4– 37.3 mg/L. Relative standard deviation (n = 5) for peak area is under 3.0 %. The method has been successfully applied to determine imidazolium cations in ionic liquids synthesized by analytical chemistry lab, the results are accurate. And these results are helpful for further investigations to apply monolithic columns.Finally, a gradient and fast ion-pair chromatographic method was established for determination of five imidazolium ionic liquid cations using a silica-based monolithic column and ultraviolet detection. The effects of eluent type and concentration, acetonitrile concentration, column temperature and flow rate on retention times of the cations were investigated. The best gradient condition was determined. Detection limits for the cations were 0.26– 1.61 mg/L. Relative standard deviations (n = 5) for peak areas were less than 0.5 %. The method has been successfully applied to the determination of two ionic liquids synthesized by analytical chemistry lab. Recoveries of the cations after spiking were 96.8 %– 101.9 %. Using a monolithic column, the analysis time was reduced, and a rapid method for analysis of imidazolium cations was established.