Fast Adsorptive Stripping Voltammetry of Iron in Oxygenated Seawater

Abstract

A fast adsorptive stripping voltammetric procedure for the determination of ultratrace amounts of iron in unpurged oceanic waters is reported. The method is based on that developed by van den Berg et al. [l]. It was modified to increase the sensitivity, to measure in the presence of oxygen and to reduce drastically the analysis time at the ultratrace level (pM). The scan rate, pH and concentrations of reagents were optimized to avoid interferences using background correction. The catalytic effect of the hydrogen peroxide was not found using high scan rate. The instability of the peak was related to colloidal iron. Acidified or heated samples showed stable peaks. The method is insensitive to the turbulence of the solution during the scan. The reproducibility (±40 pM) and detection limits (120 pM) of the method were calculated using 60s deposition time and oceanic waters (600pM). The detection limit can be lowered to 70 pM using 3 min accumulation.