VARIABILITY OF THE SLOPES OF STANDARD ADDITION PLOTS IN THE ANALYSIS OF COPPER IN SEAWATER BY ANODIC-STRIPPING VOLTAMMETRY

Copper in seawater was analyzed with a 'hybrid' mercury film-glassy ca rbon electrode using linear sweep, square wave and differential pulse anodic stripping voltammetry. The analyses were made in HCl (pH 2) and ethylenediamine (EN)-spiked seawater (9 < pH < 10), with and without purging the sample of dissolved oxygen. The relative slopes of the sta ndard addition plots were used to determine the effect of mode and med ia alteration on the results. Square-wave voltammetry in EN-altered se awater, without oxygen purging, was found to be not only the most prac tical technique, but also highly sensitive. The 'chemistry' of the oxi dation reaction during the stripping step was found to affect the expe rimental results markedly. For this reason, the peak current is an exp erimentally dependent measure of the ion flux, both, into and out of t he electrode.