Determination of inorganic anions by ion chromatography using a graphitized carbon column dynamically coated with cetyltrimethylammonium ions

Abstract

The simultaneous determination of inorganic anions by ion chromatography using a dynamically coated graphitized carbon column with cetyltrimethylammonium (CTA) ions was investigated with suppressed conductivity detection. Column preparations with CTA and sodium carbonate–sodium hydrogencarbonate concentration in the eluent were examined to optimize the separation of seven common anions (F −, Cl −, NO 2 −, Br −, NO 3 −, HPO 4 2− and SO 4 2−). Calibration curves were linear from 0.5 to 5 μg/ml for F −, from 1.0 to 10 μg/ml for Cl −, from 1.5 to 15 μg/ml for NO 2 −, from 2.0 to 20 μg/ml for Br − and NO 3 −, from 5.0 to 50 μg/ml for HPO 4 2− and from 3.0 to 30 μg/ml for SO 4 2− with correlation coefficients ( r) of 0.999 or better. The relative standard deviations of peak areas were between 0.3 and 0.9% for 10 repeated measurements. The application of this newly developed method was demonstrated by the determination of inorganic anions in the water for pharmaceutical purposes. Using CTA-Br as the coating agent, a permanently coated ion-exchange column was obtained, which allowed efficient separations of seven anions without adding any coating agent to the eluent.