Polarographic detection by reverse-pulse amperometry in cation-exchange chromatography without interference from dissolved oxygen

Abstract

Reverse-pulse amperometry (r.p.a) at a static dropping mercury electrode (SDME) is applied for detection in high-performance cation-exchange chromatography for Cu 2+, Zn 2+, Ni 2+, Pb 2+, Cd 2+ and Fe 2+ using a tartrate eluent (pH 3.5–4.5). The technique of r.p.a. as applied eliminates the need for removal of dissolved oxygen because the anodic signals for oxidation of the reduction products are measured at a potential at which oxygen is not electroactive. Typical detection limits ( S/N = 2) for a 100-μl sample are illustrated by the values 13 μg l −1 Zn 2+ (1.3 ng) and 64 μg l −1 Cu 2+ (6.4 ng). The detection limits are decreased by ca. 2 orders of magnitude by using preconcentration from a 10.0-ml sample on a cation-exchange fore-column.