Abstract: A method was developed for the simultaneous determination of hexafluorophosphate and other trace impurity anions in ionic liquids by ion chromatography (IC). The sample was diluted with 70% (v/v) acetonitrile, filtrated by 0.22 μm nylon filter membrane, and then analyzed by IC. The analytical column was Dionex IonPac AS22 (250 mm×4 mm), carbonate-acetonitrile (70:30, v/v) was used as the eluent at a flow rate of 1.0 mL/min. The detection was performed by a Dionex DS6 conductivity detector. The quantitive analysis of external standard calibration curves was used. The linear ranges of the method for F~, Cl~, Br~ and PF~6 were 0.5~50 μg/L (r0.9999), 10~200 μg/L (r0.9998), 10~200 μg/L (r0.9999) and 0.9~45 mg/L (r0.9998), respectively. The average recoveries were 94.5%~100.5% with the relative standard deviations of 0.63%~1.03%. The detection limits (S/N3) were 0.5 μg/L, 2.0 μg/L, 5.0 μg/L and 0.9 mg/L for F~, Cl~, Br~ and PF~6, respectively. The method has been applied to determine hexafluorophosphate and other trace impurity anions in ionic liquids with satisfactory results.

Key words: anion, hexafluorophosphate, ionic liquids (ILs) , ion chromatography (IC)