Electroanalytical Determination of Trace Chloride in Room-Temperature Ionic Liquids

摘要

The electroanalytical quantification of chloride in [C_(4)mim]-[BF_(4)], [C_(4)mim][NTf_(2)], and [C_(4)mim][PF_(6)] ionic liquids has been explored using linear sweep and square wave voltammetry. Cathodic stripping voltammetry at a silver disk electrode is found to be the most sensitive. The methodology is based on first holding the potential of the electrode at +2.0 V (vs Ag wire), to accumulate silver chloride at the electrode. On applying a cathodic scan, a stripping wave is observed corresponding to the reduction of the silver chloride. This stripping protocol was found to detect ppb levels of chloride in [C_(4)mim][BF_(4)], [C_(4)mim][NTf_(2)], and [C_(4)mim][PF_(6)]. Although other methods for chloride have been reported for [BF_(4)]~(-)- and [PF_(6)]~(-)-based ionic liquids, no methods have been reported for [NTf_(2)]~(-) ionic liquids.