Mutual interference problems in the simultaneous voltammetric determination of trace total mercury(ii) in presence of copper(ii) at goldelectrode. Applications to environmental matrices

Abstract

The present work describes and discusses the possible interference problems in the voltammetric determination of ultra-trace concentrations of Hg(II) in the presence of Cu(II) at a gold electrode, using three different supporting electrolytes: 0.1 mol L⁻¹ HClO₄, 0.01 mol L⁻¹ EDTA-Na₂ + 0.06 mol L⁻¹ NaCl + 2.0 mol L⁻¹ HClO₄ and 0.1 mol L⁻¹ KSCN + 0.001 mol L⁻¹ HClO₄. The square wave anodic stripping voltammetric (SWASV) measurements were carried out using a conventional three-electrode cell, with a gold electrode (GE) as the working electrode, and platinum wire and Ag|AgCl|KCl_sat as auxiliary and reference electrodes, respectively. The analytical procedure was validated by the analysis of the standard reference materials Estuarine Sediment BCR-CRM 277, River Sediment BCR-CRM 320 and Mercury in Water NIST-SRM 1641d. In the presence of reciprocal interference, the standard addition method considerably improved the resolution of the voltammetric technique even in the case of very high concentration ratios of both metals. The analytical procedure was transferred and applied to sediments and sea waters sampled in a lagoon ecosystem connected to the Adriatic Sea and located in proximity to the Ravenna area (Italy).