Determination of inorganic anions by non-suppressed ion chromatography with indirect ultraviolet absorption detection

Abstract

Reversed-phase high-performance liquid chromatography (HPLC) using a hexadecyltrimethylammonium bromide (CTAB) conditioned stationary phase is shown to provide efficient separation of iodate, phosphate, bromate, chloride, nitrite, bromide, nitrate and chlorate in 11 min. The anions were detected using an eluent containing sodium hydrogen phthalate by the indirect ultraviolet absorption (IUA) technique. The mechanism of separation of the anions is attributed to their interaction with the surface electrical double layer (formed by the initial adsorption of CTAB on the stationary phase) followed by conditioning with sodium hydrogen phthalate. Systems peaks could be induced by increasing the pH or the ionic strength of the eluent.

The application of ion chromatography with IUA detection to the determination of anions is demonstrated via the determination of nitrate and chloride in both a domestic water sample and a river water sample. The limits of detection for nitrate and chloride were 3 and 4 nmol of anion injected, respectively.