SIMULTANEOUS AMPEROMETRIC AND POTENTIOMETRIC DETECTION OF INORGANIC ANIONS IN FLOW SYSTEMS USING PLATINUM AND SILVER SILVER-CHLORIDE ELECTRODES

Platinum and silver/silver chloride electrodes were evaluated for elec trochemical detection (amperometry and potentiometry, respectively) of inorganic anions in flow systems. In flow injection analysis, a linea r response over three decades and detection limit of 1x10(-7) M for I- and NO2- were obtained at an applied potential of +0.9 V (vs. Ag/AgCl ) in 30 mM phosphate buffer at pH 3.0 as carrier. A silver/silver chlo ride electrode responded potentiometrically to halides and pseudo-hali des in this buffer with a detection limit of 1x10(-5) M. The detector, which included both detection systems, was coupled with ion chromatog raphy. Following separation by anion-exchange chromatography with 40 m M phosphate buffer at pH 4.5 as eluent, Cl-, Br-, I-, SCN-, and S2O32- were determined potentiometrically with a detection limit of 1x10(-5) M, and, simultaneously, NO2-, Br-, I-, and SCN- were determined amper ometrically with a detection limit of 1x10(-6)M. Ion-interaction chrom atography with an eluent of 20 mM phosphate at pH 5.0 containing 5 mM tetrabutylammonium hydroxide separated and detected Br-, NO2- and SCN- .