Determination of ionic liquid cations in soil samples by ultrasound-assisted solid-phase extraction coupled with liquid chromatography-tandem mass spectrometry

摘要

Liquid chromatography-tandem mass spectrometry coupled with an ultrasonic-assisted extraction and solid phase extraction procedure has been investigated for the separation and detection of imidazolium, pyridinium, pyrrolidinium, ammonium and phosphonium-based ionic liquid (IL) cations in soil samples. First, the samples were extracted with acetonitrilea€“0.2 mol La?’1 ammonium chloride solution (8:2, v/v; pH 3) using an ultrasonic assisted extraction procedure and then eluted on a Strata-X-CW solid-phase extraction column. The target compounds were effectively separated with an Agilent SB-C18 (1.88 ??m, 3.0 mm ?— 100 mm) chromatographic column by gradient elution, in which acetonitrilea€“water (containing 0.1% formic acid) acted as the mobile phase. The IL cations were determined by electrospray positive ionization (ESI+) combined with multiple reaction monitoring (MRM) mode, and quantified by the matrix-matched external standard method. The limits of detection (LODs) ranged from 0.15 to 2.88 ng ga?’1 and the limits of quantification (LOQs) from 0.50 to 9.50 ng ga?’1. The average recoveries of the twenty-three IL cations in soil samples were in the range of 69.3a€“106.8%, with relative standard deviations of 2.17a€“12.1%. This assay showed greater sensitivity and accuracy, to meet the requirements of the determination of IL cations in soil.