Analytical Sciences

Rapid and Simultaneous Determination of Tetrafluoroborate, Thiocyanate and Hexafluorophosphate by High-Performance Liquid Chromatography Using a Monolithic Column and Direct Conductivity Detection

Ling YANG, Hong YU, and Yaqin WANG

College of Chemistry and Chemical Engineering, Harbin Normal University, Harbin 150025, China

A method was developed for fast and simultaneous determination of tetrafluoroborate (BF₄⁻), thiocyanate (SCN⁻) and hexafluorophosphate (PF₆⁻) by high-performance liquid chromatography using a silica-based monolithic column and direct (non-suppressed) conductivity detection. Chromatographic separation was performed on a Chromolith Speed ROD RP-18e column with tetrabutylammonium hydroxide (TBA) + citric acid + acetonitrile as eluent. The effects of the types of eluent, TBA concentration, acetonitrile volume fraction, eluent pH, column temperature and flow rate on the retention of anions were investigated. The optimized chromatographic conditions were selected. Under the optimal conditions, the baseline separation of BF₄⁻, SCN⁻ and PF₆⁻ was achieved without any interference by other anions (F⁻, Cl⁻, Br⁻, I⁻, NO₃⁻, ClO₃⁻ and SO₄²⁻). The detection limit (S/N = 3) was 0.42, 0.46 and 1.42 mg L⁻¹ for BF₄⁻, SCN⁻ and PF₆⁻, respectively. The present method was successfully applied to the determination of BF₄⁻, SCN⁻ and PF₆⁻ in ionic liquids.

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