DETERMINATION OF INORGANIC ANIONS IN SALT-SOLUTIONS BY ION CHROMATOGRAPHY USING C18 REVERSED-PHASE COLUMNS COATED WITH CETYLTRIMETHYLAMMONIUM

A simple and sensitive method using ion chromatography is described for the determination of I-, SCN-, NO2- and S2O32- as impurities in inorganic analytical-reagent grade chemicals. Aqueous solutions of individual salts containing matrix-anions (5-20 g/l) were prepared and analyzed directly for trace impurities. Good chromatograms of trace anions were obtained without interference by matrix ions. C18 reversed-phase columns coated with cetyltrimethylammonium (CTA+), with either high or low capacity, a mobile phase mixture (pH 5.8) of sodium chloride (0.1 M) and sodium phosphate buffer (0.005 M), and ultraviolet (225 nm) and amperometric (+ 1.0 V vs. Ag/AgCl) detection systems were used. The detection limits for different impurities in the solutions were 0.002-0.06 mg/l.