Determination Of Pyrrolidinium, Morpholinium And Transition Metal Cations By Ion Chromatographyindirect Ultraviolet Detection

An investigation into analysis of pyrrolidiunium, morpholinium ionic liquid cations and transition metal cations by ion chromatography was carried out. The purpose of this research is to develop accurate, fast and simple methods to determine ionic liquid cations, and expand ion chromatography with indirect UV detection to analysis of ionic liquid cations and the transition metal ions. This study mainly contains three parts:The first part, an analytical method was developed for the determination of pyrrolidiunium ionic liquid cations by ion chromatography with indirect ultraviolet detection. Chromatographic separation of pyrrolidiunium cations was performed on a sulfonic acid base cation exchange column using imidazolium ionic liquid- organic solvent as mobile phase. The effects of the kinds and concentrations of background ultraviolet absorption reagents, detection wavelength, the kinds and concentrations of organic solvents and column temperature on the separation and determination of pyrrolidinium cations were investigated. The retention rules of the cations under different chromatographic conditions were discussed. The result indicated that, the successful separation of the three pyrrolidinium cations within 18 min was achieved using the optimized eluent of 0.8 mmol/L 1-ethyl-3-methyl-imidazolium tetrafluoroborate/methanol(95/5,v/v) at a detection wavelength of 220 nm and a column temperature of 30℃ and a flow rate of 1.0 mL/min. Under the conditions, the detection limits(S/N = 3) of three pyrrolidinium cations were 0.34, 0.48 and 0.83 mg /L respectively, Relative standard deviations(n = 5) for peak area and retention time were less than 1.1%. The method was applied in the determination of pyrrolidinium ionic liquids synthesized in chemical laboratory with spiked recoveries of 94.0% to 98.7%. The method is accurate, reliable, could meet the requirements for quantitative analysis.The second part, a rapid analytical method of ion chromatography with indirect ultraviolet detection was developed to determine morpholinium ionic liquid cations. Chromatographic separation of morpholinium cations was performed on a sulfonic acid base cation exchange column using imidazolium ionic liquid- organic solvent as mobile phase. The effects of chromatographic columns, ultraviolet absorption reagents, imidazolium ionic liquids, detection wavelength, organic solvents, pH values of the mobile phase and column temperature on the retention of morpholinium cations were investigated. Using the eluent of 0.8 mmol/L 1-ethyl-3-methyl-imidazolium tetrafluoroborate / acetonitrile(95/5, v/v) at a detection wavelength of 220 nm, the detection limits(S/N = 3) of two morpholinium cations were 0.29 and 0.44mg/L, respectively. Relative standard deviations(n = 5) for peak area and retention time were less than 3.3%. The method was applied in the determination of morpholinium ionic liquids synthesized in chemical laboratory. Recoveries determined by standard addition method were 93.8% to 99.0%. The method simple, fast, and make the quantitative analysis of morpholinium cations possible.The third part, on the basis of the former two studies, the exchange chromatography with indirect ultraviolet detection method for the determination and separation is applied to analyze three kinds of transition metal cations(Cr3+, Mn2+, Zn2+). This research adopts the carboxylic acid type cation exchange column, with imidazolium ionic liquid + oxalic acid as mobile phase. Different kinds and concentrations of background ultraviolet absorption reagents, the kinds and concentrations of acids, the kinds of organic solvent, detection wavelength, chromatographic column temperature on the separation and determination of three kinds of transition metal ions were investigated, the effect of retention rules are also discussed, the results showed that the tendency at 0.7 mmol/L1-ethyl-3-methyl-imidazolium tetrafluoroborate + 0.7 mmol/L oxalic acid as mobile phase, detection wavelength of 220 nm, flow rate of 1.0 mL/min, Cr2+, Mn2+, Zn2+ within 20 min to baseline separation. Detection limit(S/N = 3) were 0.13, 0.13, and 0.18 mg/L, the peak area and relative standard deviation of retention time of below 2.0%(n = 5).This method is accurate, reliable and can meet the requirements of quantitative analysis.