Speciation of trace metals in seawater by anodic stripping voltammetry: Critical analytical steps

The speciation of trace metals in seawater based on the voltammetric (DPASV) titration of ligands by metal addition is considered. The method allows the determination of the total metal amount, the labile fraction, the ligand concentration and the related conditional stability constant. Analytical problems related to sample contaminations during sampling, filtration and storage, displacement of complexing equilibria in freeze storage, the kinetics of the reaction of complexation and the potential kinetic lability of organic complexes are discussed and possible solutions presented. Data on quality control tests carried out to verify the accuracy of the laboratory procedure for trace metal determination in seawater are reported.