Simultaneous amperometric and potentiometric detection of inorganic anions in flow systems using platinum and silver/silver chloride electrodes

Abstract

Platinum and silver/silver chloride electrodes were evaluated for electrochemical detection (amperometry and potentiometry, respectively) of inorganic anions in flow systems. In flow injection analysis, a linear response over three decades and detection limit of 1 × 10 −7 M for I − and NO 2 − 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 chloride electrode responded potentiometrically to halides and pseudo-halides in this buffer with a detection limit of 1 × 10 −5 M. The detector, which included both detection systems, was coupled with ion chromatography. Following separation by anion-exchange chromatography with 40 mM phosphate buffer at pH 4.5 as eluent, Cl −, Br −, I −, SCN −, and S 2O 3 2− were determined potentiometrically with a detection limit of 1 × 10 −5 M, and, simultaneously, NO 2 −,Br −, I −, and SCN − were determined amperometrically with a detection limit of 1 × 10 −6 M. Ion-interaction chromatography with an eluent of 20 mM phosphate at pH 5.0 containing 5 mM tetrabutylammonium hydroxide separated and detected Br −, NO 2 − and SCN −.