J. Donat, K. Bruland
Feb 1, 1988
Citations
5
Influential Citations
145
Citations
Quality indicators
Journal
Analytical Chemistry
Abstract
A highly sensitive voltametric technique was developed for the direct determination of cobalt and nickel in seawater at picomolar and nanomolar concentrations, respectively. Cyclohexane-1,2-dione dioxime (nioxime) complexes of Co(II) and Ni(II) were concentrated from 10 mL of sample onto a hanging mercury drop electrode by controlled adsorption and the current resulting from reduction of Co(II) and Ni(II) was measured by differential pulse cathodic stripping voltametry. Detailed experiments were conducted to determine the optimal ligand type and concentration, buffer type and concentration, pH, and adsorption potential. Maximum sensitivity was obtained by using a nioxime concentration of 1 x 10/sup -4/ m, a HEPES buffer concentration of 0.03 m, a solution pH of 7.6, and an adsorption potential of -0.6 V. Replicate analyses of seawater reference materials yielded excellent agreement with certified values. Analytical precision for Co and Ni at coastal and open ocean concentrations was approximately +/-5% relative standard deviation. Detection limits for Co and Ni depend upon reagent blanks and are 6 pM and 0.45 nM, respectively, for 15-min adsorption periods.