Rapid Determination of Pyridinium Ionic Liquid Cations by Ion-Pair Chromatography Using a Reversed Phase Silica-Based Monolithic Column

Abstract

A fast and gradient ion-pair chromatographic method was developed for the determination of four pyridinium ionic liquid cations using a reversed phase silica-based monolithic column and ultraviolet detection.Chromatographic separations were performed on a Chromolith Speed ROD RP-18e column with 1-heptanesulfonic acid sodium solution(pH 4.0 adjusted by citric acid)+acetonitrile as eluent and gradient elution.The effects of chromatographic column,eluent,flow rate and column temperature on retention and separation of the cations were investigated.The retention rules of pyridinium cations on the monolithic column were discussed.The retention of imidazolium cations accords with carbon number rule.The gradient elution procedure was optimized using 1.0 mmol/L 1-heptanesulfonic acid sodium(pH 4.0)+acetonitrile as eluent,and simultaneous separation of four pyridinium cations within 7 min was achieved under the optimum gradient conditions.Detection limits(S/N=3) for the cations were 0.05-0.17 mg/L.Relative standard deviations(n=5) for peak areas were less than 0.6%.The method has been applied to analyze the ionic liquid synthesized by chemical laboratory and sewage water with spiked recoveries of 95.7%-99.0%.The method is accurate,reliable and rapid,and has better practicability.