Abstract: A method was developed for the simultaneous determination of trifluoroacetate, tetrafluoroborate and halide ions (F~, Cl~, Br~) by ion chromatography with direct conductivity detection. The chromatographic separation was performed on a Shim-pack IC-A3 anion-exchange column with potassium biphthalate, phthalic acid+tris(hydroxymethyl)-aminomethane, and p-hydroxybenzoic acid+tris(hydroxymethyl)-aminomethane+boric acid as eluent, separately. The effects of the nature of eluent, eluent concentration, acetonitrile concentration and column temperature on the separation and the retention factors of the anions were investigated. The optimized chromatographic conditions for the determination of the anions were as follows: 1.2 mmol/L potassium biphthalate as eluent, a column temperature of 45 ℃ and a flow rate of 1.0 mL/min. Under the optimal conditions, the anions were baseline separated. Moreover, the symmetries of peaks were better. The limits of detection (S/N=3) for the anions were in the range of 0.01~0.50 mg/L. The relative standard deviations (RSDs) of the chromatographic retention time and peak area for the anions were not more than 0.2% and 1.2% (n=5), respectively. The method has been applied to the determination of trifluoroacetate, tetrafluoroborate and halide ions in ionic liquids. The spiked recoveries of the anions were from 98.0% to 103.2%. The method is simple, accurate and reliable, and has better practicability.

Key words: halide ions, ionic liquid , tetrafluoroborate, trifluoroacetate, ion chromatography