A new mercury drop electrode for trace metal analysis

A new mercury drop electrode, model-1 (MDE-1, Eco Chemie, Utrecht, Netherlands) is described. The sensitivity and the reproducibility of the electrode were tested for the determination of dissolved trace metals in natural aquatic systems using differential pulse anodic stripping voltammetry (ASV). The measurements were performed at pH=7.8 using a quartz cell, with a plastic stirrer and a glass reference electrode. The results obtained showed significant adsorption of the dissolved trace metal. The adsorption mainly takes place at the surface of the cell assembly (a plastic stirrer and a reference electrode made of glass), whereas only 1.5% of dissolved copper(II) is adsorbed on the walls of the quartz cell. The adsorption of trace metals is significantly suppressed when the plastic stirrer and the sinter glass tip of the reference electrode are made of quartz. The reproducibility of the current response of the repetitive measurements of anodic peak currents of the acidic solution for the concentration range between 10(-7) and 2x10(-10) M Cd2+ showed variation coefficients from 0.7% to 3.5%, respectively. The MDE-1 detection limit of 2.5x10(-11) M Cd2+ was obtained under the given experimental conditions.