Simultaneous Determination of Trifluoromethanesulfonate, Tetrafluoroborate and Common Inorganic Anions by Ion Chromatography

A method was developed for the determination of trifluoromethanesulfonate, tetrafluoroborate and common inorganic anions by ion chromatography with direct conductivity detection. Chromatographic separation was performed on a Shim-pack IC-A3 anion exchange column using p-hydroxybenzoic acid + tris (hydroxymethyl)-aminomethane + boric acid, phthalic acid + tris (hydroxymethyl)-aminomethane, and potassium biphthalate as eluent, respectively. The effects of the types of eluent, eluent concentration and column temperature on separation and retention 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, column temperature of 30 degrees C and flow rate of 1.0 mL/min. Under these conditions, the anions were in baseline separation. Moreover, the symmetry of peaks was better. Detection limit (S/N = 3) for the anions was in range of 0. 02 - 1. 88 mg/L. The relative standard deviations (RSD) of the chromatographic retention time and peak areas for the anions were not more than 0.17% and 2.05% (n = 5), respectively. The method has been applied to the determination of trifluoroacetate, tetrafluoroborate and common anions in ionic liquids. The recoveries of the anions after spiking were from 97. 0 % to 102. 8 %. The method is simple, accurate, reliable and practical.