Reversed-phase ion-pair solid-phase extraction and ion chromatography analysis of pyrrolidinium ionic liquid cations in environmental water samples

A method of reversed-phase ion-pair solid-phase extraction combined with ion chromatography for determination of pyrrolidinium ionic liquid cations (N-methyl-N-ethyl pyrrolidinium, N-methyl-N-propyl pyrrolidinium, and N-methyl-N-butyl pyrrolidinium) in water samples was developed in this study. First, ion-pair reagent sodium heptanesulfonate was added to the water samples after static, centrifugation and filteration. Then, pyrrolidinium cations in the samples were enriched and purified by a reversed-phase solid-phase extraction column, and eluted from the column with methanol aqueous solution as eluent. Finally, the eluate collected was analyzed by ion chromatography. The separation and direct conductivity detection of these pyrrolidinium cations by ion-exchange column using 1.0 mM methanesulfonic acid (in water)/acetonitrile (97:3, v:v) as mobile phase was achieved within 10 min. By using this method, pyrrolidinium cations in Songhua River and Hulan River were successfully extracted with the recoveries ranging from 74.2 to 97.1% and the enrichment factor assessed as 60. Pyrrolidinium cations with the concentration of 0.001-0.03 mg/L can be enriched and detected in the water samples. The developed method for the determination of pyrrolidinium ionic liquid cations in water samples is simple and reliable, which provides a reference for the study of the potential impact of ionic liquids on the environment.