[Determination of piperidinium ionic liquid cations by ion-pair chromatography-indirect ultraviolet detection]

A method was developed for the determination of piperidinium cations by ion-pair chromatography with indirect ultraviolet detection. Chromatographic separation was performed on a reversed-phase C18 column using background ultraviolet absorption reagent-ion-pair reagent/organic solvent as mobile phase. The effects of the background ultraviolet absorption reagent, detection wavelength, ion-pair reagent, organic solvent, column temperature and flow rate on the determination of piperidinium cations were investigated and the retention rules were studied. The optimized chromatographic conditions for the determination of piperidinium cations were as follows: mobile phase, 0.5 mmol/L 4-aminophenol hydrochloride-0.1 mmol/L 1-heptanesulfonic acid sodium aqueous solution/methanol (80:20, v/v); detection wavelength, 210 nm; column temperature, 30 degrees C; flow rate, 1.0 mL/min. Under these conditions, the three piperidinium cations were baseline separated within 4 min. The detection limits (S/N = 3) of the piperidinium cations were 0.137-0.545 mg/L. The relative standard deviations (n = 5) for peak area and retention time were 0.72% and 0.37% respectively. The method has been successfully applied to the determination of piperidinium cations in ionic liquids synthesized by chemistry laboratory. The recoveries of piperidinium cations after spiking were 97.0%-98.4%. The method is simple, rapid, reproducible, linear, and can meet the quantitative analysis requirement for the determination of piperidinium cations.