DETERMINATION OF COMPLEXING ABILITY OF NATURAL LIGANDS IN SEAWATER FOR VARIOUS METAL-IONS USING ION-SELECTIVE ELECTRODES

A newly developed method Is presented for the measurement of the ability of organic ligands in seawater to form complexes with metal ions. Organic ligands (nominal molecular weight ≥1000) are concentrated from seawater and desalted by lyophilizatlon and dialysis. The concentrated solution of natural ligands Is electrodialyzed with ethylenediaminetetraacetic acid to remove metal ions. The demetalized ligands obtained In this way are titrated with a metal ion to determine the complexing ability of the natural ligands. The advantages of this method are as follows: the formation of a complex between organic ligands and a specific metal ion can be studied without consideration of simultaneous side-reactions; samples from different sources (saline and freshwater, biological, sedimentary, etc.) can be compared on the same basis; repeated measurements can be made with the same sample after removal of the exogenously added metal ions. The ability of natural ligands in seawater to form complexes with copper(II) and cadmium(II) is discussed. © 1990, American Chemical Society. All rights reserved.