SELECTIVE DETERMINATION OF TRACES OF COPPER BY ADSORPTIVE ACCUMULATION OF COPPER(I) BENZOTRIAZOLATE, TRANSIENT AMALGAMATION AND ANODIC-STRIPPING VOLTAMMETRY

Anodic stripping voltammetry with adsorptive accumulation of amalgam f orming metals is proposed and demonstrated for the determination of tr aces of copper ions in, the presence of benzotriazole, HBTA (an excell ent corrosion inhibitor for copper). The accumulation of the metal ion s is accomplished, as customary, by adsorption on the mercury electrod e of a coordination compound with a suitable ligand. Specifically, cop per(II) is reduced to copper(I) and accumulated as the Cu(I)BTA comple x on a hanging mercury drop electrode at 0.0 V vs SCE, under convectio n. Subsequently, copper(I) is reduced to the amalgam by applying a pot ential step to -0.4 V during 15 s or less. Finally, the potential is s canned in the positive direction and the differential pulse anodic pea k of the re-oxidation of Cu(Hg) to Cu(I)BTA is recorded. A 2 min accum ulation period provides a detection limit of 3 x 10(-9) M and an analy tical curve linear up to 8 x 10(-7) M. Accumulation for 10 min (or mor e) lowers the detection limit to 8 x 10(-10) M (or lower). The new mod e opens alternatives to improve the selectivity of cathodic stripping methods involving amalgam forming metals, and to reconsider ligands th at give rise to unsatisfactory cathodic stripping peaks, such as HBTA. (C) 1998 Elsevier Science Ltd. All rights reserved.