Comparison of differential pulse anodic stripping voltammetry and spectrofluorometry for determination of complexes between copper and organic matter in interstitial waters extracted from marine sediments

Abstract

Differential pulse anodic stripping voltammetry (DPASV) and fluorescence quenching are methods that allow measurement of complexing capacities and conditional stability constants of complexes in natural waters. Whereas the electrochemical measured signal reflects the presence of labile copper in solution, spectrofluorometry leads to an estimation of the uncomplexed fluorescent ligands. Interstitial waters extracted from estuarine and unpolluted marine sediments, as well as from sediments near urban outfall, contain high concentrations of organic matter, and their complexing capacity, as found by DPASV, often exceeds 1 μmol l −1. Furthermore, stripping curves are complex and the determination of stability constants is possible only under specific conditions. We have compared both methods by working on fulvic acid solutions and natural interstitial waters. Some correlation between the results of the two methods has been found, and it has been concluded that these methods are favourable for complementary study of interstitial waters with high organic matter content. Also, this gives a better interpretation of spectrofluorometric results versus dissolved organic carbon in natural waters.