Optimization of solid phase extraction and simultaneous determination of trace anions in concentrated hydrofluoric acid by ion chromatography

A sensitive method to detect trace anions in hydrofluoric acid (HF) by solid-phase extraction (SPE) clean-up and ion chromatography (IC) was described. Fluoride in HF solution was eliminated with solid-phase extraction, and residual fluoride, acetate, chloride, bromide, nitrate, phosphate and sulfate were consecutively separated with IC. The SPE parameters (selection of adsorbent, sample volume and pH, elution solvent and its volume) were optimized and selected. The removal effect of fluoride in HF solution was the best on Oasis WAX column, and the optimum conditions (1.0 mL of 25 % HF solution and 50 mM ammonium acetate 5 mL as elution solvent) were established by the variation of parameters. Under the established condition, the method detection limits of chloride, bromide, nitrate, phosphate, and sulfate were 0.04+/-0.30 mu g/L in 25 % HF solutions (w/w) and the relative standard deviation was less than 5 % at concentrations of 20.0 and 40.0 mu g/L. The concentrations of anions in a 25 % HF had detectable levels of 4.2 to 47.5 mu g/L. The method was sensitive, reproducible and simple enough to permit the reliable routine analysis of anions in HF solution used in the process of producing semiconductors.