Determination Of Pyrrolidinium Ionic Liquid Cations By Ion-pair Chromatography

An investigation into analysis of pyrrolidinium ionic liquids cations by ion-pairchromatography with indirect ultrabiolet detection was carried out. The purpose of thisresearches is to develop simple, rapid, reliable, accurate and sensitive methods todetermine pyrrolidinium cations which have no ultrabviolet absorbtion by ion-pairchromatography. This study mainly contains three parts:1. A method was developed on ion-pair chromatographic with indirect ultravioletdetection which using4-amiophenol hydrochloride as background ultraviloet absorbingreagents. The analytes were separated using a mobile phase of background ultravioletabsorbing reagent ion-pair reagent organic solvent on a reversed-phase silica-basedmonolithic column. The effects of the mobile phase, detection wavelength, columntemperature and flow rate on the separation and determination of the cations wereinvestigated. The optimized chromatographic conditions were as follows:80%(0.5mmol/L4-amiophenol hydrochloride0.1mmol/L1-heptanesulfonic acid sodium)aqueous solution20%(v/v)methanol as mobile phase, detection wavelength230nm,column temperature30oC, flow rate2.0mL/min. Under these conditions, the retentiontimes of N-methyl, ethyl-pyrrolidinium, N-methyl, propyl-pyrrolidinium and N-methyl,butyl-pyrrolidinium are less than1.6min and the baseline separation were achieved.The detection limits (S/N=3) were0.020.07mg/L. Relative standard deviations (n=5)of chromatographic peak area were less than0.45%. The proposed method was appliedto the determination of cations in three pyrrolidinium ionic liquids synthesized bylaboratory. The spiked recoveries were98%. The method is rapid, simple, accurate,reliable and practical.2. A method was developed on ion-pair chromatographic with indirect ultravioletdetection which using imidazolium ionic liquids as background ultraviloet absorbingreagents. Chromatographic separation of pyrrolidinium cations was performed on areversed-phase C18column using imidazolium ionic liquid ion-pair reagent organicsolvent as mobile phase. The effects of the mobile phase on the retention ofpyrrolidinium cations were investigated. The imidazolium ionic liquid in mobile phaseis both background ultraviolet absorption reagents of indirect ultraviolet detection andthe effective component to improve the separation of pyrrolidinium cations. Under the optimized chromatographic conditions as follows:80%(1.0mmol/L1-propyl-3-methyl-imidazolium tetrafluoroborate0.15mmol/L1-heptanesulfonicacid sodium aqueous solution, pH4.5adjusted with acetic acid)20%(v/v)methanol,detection wavelength220nm, column temperature30oC, flow rate1.0mL/min, thebaseline separation of N-methyl, ethyl-pyrrolidinium, N-methyl, propyl-pyrrolidiniumand N-methyl, butyl-pyrrolidinium were achived and the retention time is less than13min. The detection limit (S/N=3) for the cations were0.2,0.4and1.1mg/L,respectively. Relative standard deviations (n=5) for chromatographic peak area were0.2%,0.6%and1.5%. The method has been successfully applied to the determinationof ionic liquids synthesized by laboratory and the spiked recoveries were92%97%.The method is simple, accurate, reliable, and parctial.3. A method was developed on a monolithic column for the fast determination ofpyrrolidinium cations by ion-pair chromatography with undirect ultraviolet detectionwhich using imidazolium ionic liquids as mobile phase addititives. Chromatographicseparation was performed on a reversed-phase silica-based monolithic column usingionic liquids ion-pair reagents organic solvents as mobile phase. The effects of themobile phase, column temperature, flow rate on the retention of pyrrolidinium cationswere invertigated. The optimized chromatographic conditions were as follows:91%(0.7mmol/L1-propyl-3-methyl-imidazolium tetrafluoroborate0.2mmol/L1-heptanesulfonic acid sodium aqueous solution, pH4.5adjusted with acetic acid)9%(v/v)methanol, detection wavelength210nm, column temperature30oC, flow rate4.0mL/min. Under these conditions, N-methyl, ethyl-pyrrolidinium, N-methyl,propyl-pyrrolidinium and N-methyl, butyl-pyrrolidinium were successfully separatedwithin2.5min, the detection limit (S/N=3) for the cations were0.36,0.51and1.11mg/L.Relative standard deviations (n=5) for chromatographic peak area were0.31%,0.88%and0.22%. The method has been successfully applied to the determination of ionicliquids synthesized by laboratory and the spiked recoveries were94%98%. The resultsdemonstrated that the convenience, rapidity, sensitivity and accuracy were fit for therequirements of quantitative analysis of ionic liquids.