Separation and indirect ultraviolet detection of piperidinium cations by using imidazolium ionic liquids in liquid chromatography

A method for the separation and indirect ultraviolet detection of piperidinium cations by using imidazolium ionic liquids in liquid chromatography was developed. This method uses the most common ultraviolet detector and C18 reversed-phase chromatographic column. The influences of imidazolium ionic liquids, ion-pair reagents, organic solvents, etc. on the separation and detection of piperidinium cations were investigated. The imidazolium ionic liquids in mobile phase are both the background ultraviolet absorption reagent of indirect ultraviolet detection and the active components to improve the separation of piperidinium cations. Compared with reversed-phase chromatography, reversed-phase ion-pair chromatography is a better method for the determination of piperidinium cations. The determination of N-methyl-N-propylpiperidinium (PMPI) and N-butyl-N-methylpiperidinium (BMPI) was achieved by reversed-phase ion-pair chromatography with indirect ultraviolet detection using 0.5 mmol/L 1-ethyl-3-methylimidazolium tetrafluoroborate–0.1 mmol/L sodium 1-heptanesulfonate aqueous solution/methanol (volume ratio 70–30) as mobile phase. The retention times of PMPI and BMPI were 1.96 and 2.48 min, respectively. The limits of detection for PMPI and BMPI were 0.29 and 0.53 mg/L, respectively. The linear range of the method for determination of PMPI and BMPI was 2.0–100.0 mg/L. The relative standard deviation of the method is less than 2.0%. The method has been applied to the determination of piperidinium ionic liquid samples synthesized by chemistry laboratory with satisfactory accuracy and precision. This method is simple, rapid and easy to popularize.