| An investigation into analysis of piperidinium ionic liquid cations without ultraviolet absorption by high performance liquid chromatography was carried out. The effects of different ultraviolet absorbing reagents on the determination of piperidinium ionic liquid cations, the purpose of this research is to develop simple, rapid and reliable methods to determine ionic liquid cations by high performance liquid chromatography. This study mainly contains three parts:Firstly, a method was researched for the determination of piperidinium cations by ion-pair chromatography with indirect ultraviolet detection using 4-amiophenol hydrochloride ultraviolet absorbing reagent. Chromatographic separation was performed on a reversed-phase column, the ultraviolet absorption reagent of 4-amiophenol hydrochloride has been added to the mobile phase. Chromatographic separation N-methyl, ethyl-piperidinium cation, [MEPi]+, N-methyl, propyl-piperidinium cation, [MPPi]+, N-methyl, butyl-piperidinium cation, [MBPi]+. The effects of ultraviolet absorbing reagents, ion-pair reagents, organic solvents, column temperature and flow rate on the determination of piperidinium cations were investigated. The optimized chromatographic conditions for the determination of piperidinium cations were as follows:detection wavelength 210nm, column temperature 30?, flow rate 1.0 mL/min, 0.5 mmol/L 4-amiophenol hydrochloride-0.1 mmol/L 1-heptanesulfonic acid sodium aqueous solution/methanol (80:20, v/v). Under these conditions, the baseline separated time for three kinds of piperidinium cations was 4 min. The detection limits (S/N=3) of the piperidinium cations ([MEPi]+, [MPPi]+, [MBPi]+) was 0.1-0.5 mg/L. The relative standard deviations (n= 5) for peak area and retention time were 0.72% and 0.37%. The method has been successfully applied to the determination of piperidinium cations ([MEPi]+, [MPPi]+, [MBPi]+) in ionic liquids synthesized by chemistry laboratory. Recoveries of piperidinium cations after spiking were 97%-98.4%. The method was simple, accurate and reliable.Secondly, a method was researched for the determination of piperidinium cations by ion-pair chromatography with indirect ultraviolet detection using imidazole ionic liquids ultraviolet absorbing reagent. Chromatographic separation was performed on a reversed-phase C18 column, the ionic liquid ultraviolet absorption reagent, 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIm][BF4])-ion-pair reagent organic solvent has been added to the mobile phase. Chromatographic separation [MPPi]+, [MBPi]+. The effects of detection wavelength, ion-pair reagents, organic solvents and different of imidazolium ionic liquid on the determination of piperidinium cations were investigated. The optimized chromatographic conditions for the determination of piperidinium cations were as follows the baseline separated time for two kinds of piperidinium cations [MPPi]+, [MBPi]+was 3 min. The detection limits (S/N=3) of the piperidinium cations were 0.07 mg/L and 0.16 mg/L. The relative standard deviations (n=5) for peak area and retention time were 0.22% and 0.19%. The method has been successfully applied to the determination of piperidinium cations in ionic liquids synthesized by chemistry laboratory. Recoveries of piperidinium cations after spiking were 95.54%-98.31%and 95.20%-102.95%. The method can meet the requirement for the quantitative analysis of piperidinium cations.Finally, research the effect of ultraviolet absorbing reagent on the determination of piperidinium ionic liquid cations. Chromatographic separation was performed on a reversed-phase column using ultraviolet absorbing reagent-ion-pair reagent-organic solvent as mobile phase. The effects of different the ultraviolet absorption reagents: 4-amiophenol hydrochloride and ionic liquid [EMIm][BF4] have been added to the mobile phase, different the anions on the determination of piperidinium cations were investigated. [EMIm][BF4] as the ultraviolet absorbing reagent has low detection limit, better chromatographic peak. The different anions have no effect on the determination of piperidinium cations. |
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