| In this paper,solid phase extraction(SPE)and ion chromatography(IC)were combined to analyze ionic liquid cations in environmental water.The aim is to establish an effective and convenient method for the analysis of ionic liquid cations in environmental water,and to provide a new referenced method for monitoring ionic liquids in the environment and studying their environmental impact.The main contents and results are as follows.1.The enrichment of morpholinium ionic liquid cations in environmental water by SPE and detection by ion chromatography were studied.Carboxylic acid cation exchange column was selected for chromatographic analysis.The effects of different acids,organic solvents and flow rate on the separation of morpholinium cations were investigated.The retention law of morpholinium cations was discussed.The retention law was consistent with the mechanism of ion exchange chromatography.With 5.0 mmol/L methanesulfonic acid-2%(v/v)acetonitrile as mobile phase and flow rate of 1.0 mL/min,N-methyl-N-ethyl morpholinium cation and N-methyl-N-propyl morpholinium cation were separated well within 15 min by direct conductivity detection.The environmental water samples were enriched and purified by UF-SCX sulfonic acid SPE column,and the target compounds were eluted by 0.5 mol/L phosphoric acid-sodium dihydrogen phosphate buffer solution-55% methanol.Under these conditions,good recovery and suitable enrichment factor could be obtained.The method has been applied to the analysis of three kinds of environmental water samples,which were Songhua River water,Donghu Lake water and Hulan River water.The recovery of the method was from 75.0% to 98.3%.The method is easy to operate and suitable for detecting morpholinium ionic liquid cations in environmental water.2.The enrichment of pyridinium ionic liquid cations in environmental water by SPE and detection by ion chromatography were studied.The chromatographic conditions for detecting N-ethyl pyridinium,N-butyl pyridinium and N-hexyl pyridinium cations were as follows: Shodex IC YK-421 carboxylic acid functional group cation exchange column and 3.0 mmol/L methanesulfonic acid-8% acetonitrile as mobile phase.At this point,the detection limits of three pyridinium cations were 0.16,0.29 and 0.51 mg/L,and the quantitative limits were 0.52,0.96 and 1.71 mg/L,respectively.The reproducibility and linearity were good.Ion exchange solid phase extraction was used,the impurities were washed with 10 mL 20% acetonitrile-water solution,and eluted with 5 mL 0.5 mol/L phosphoric acid-sodium dihydrogen phosphate buffer solution-55% methanol.At this point,good recovery and enrichment factors were available.The method has been applied to the analysis of actual environmental water samples,and the recovery was from 98.8% to 99.2%.It provides a new reference method for detecting pyridinium ionic liquid cations in environmental water.3.The enrichment of pyrrolidinium ionic liquid cations in environmental water by reversed phase ion pair SPE and detection by ion chromatography were studied.Firstly,ion-pair reagent sodium heptane sulfonate was added to stationary,centrifugal and filtered environmental water samples to a concentration of 0.8 mmol/L.And then purified and enriched by C18 solid phase extraction column,and eluted by 5 mL 80% methanol solution.Finally,the eluent was collected for chromatographic analysis.The separation and detection of N-methyl-N-ethyl pyrrolidinium,N-methyl-N-propyl pyrrolidinium and N-methyl-N-butyl pyrrolidinium were realized within 10 min,which by ion-exchange column with 1.0 mmol/L methanesulfonic acid-3% acetonitrile as mobile phase and conductivity detection method.The method has been applied to the separation and detection of target cations in actual environmental water samples of Songhua River and Hulan River,and the recovery was from 72.0% to 96.0%.The method is easy to operate and suitable for monitoring the pyrrolidinium ionic liquid cations in environmental water. |
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