[Simultaneous determination of hexafluorophosphate and other trace impurity anions in ionic liquids by ion...

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 microm nylon filter membrane, and then analyzed by IC. The analytical column was Dionex IonPac AS22 (250 mm x 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 PF6(-) were 0.5 - 50 microg/L (r = 0.9999), 10 - 200 microg/L (r = 0.9998), 10 - 200 microg/L (r = 0.9999) and 0.9 - 45 mg/L (r = 0.9998), respectively. The average recoveries were 94.5% - 100.5% with the relative standard deviations of 0.63% - 1.03%. The detection limits (S/N = 3) were 0.5 microg/L, 2.0 microg/L, 5.0 microg/L and 0.9 mg/L for F(-), Cl(-), Br(-) and PF6(-), respectively. The method has been applied to determine hexafluorophosphate and other trace impurity anions in ionic liquids with satisfactory results.