Pseudopolarographic determination of Cd2+ complexation in freshwater.


Journal Article

Pseudopolarography was used to detect Cd2+ complexes in samples collected at several locations along the Potomac River in June and September, 2004. Irrespective of site and sampling time, no weak inorganic Cd2+ species were present. However, up to two stable Cd(2+)-organic complexes were detected at each site. These unknown Cd2+ complexes were characterized by their half-wave potential (E1/2). The E1/2 values indicated certain Cd2+ complexes were common at different sites during each sampling but different complexes were observed in June and September. A Cd2+ chelate scale, generated from model ligands, was used to estimate the thermodynamic stability constants (K(THERM)) of the unknown complexes, which ranged from log K(THERM) = 21.5-32.0. Pseudopolarography did not recover all Cd2+ in the samples. This was partly attributed to highly stable Cd-sulfide species; owing to the presence of acid volatile sulfide at concentrations greater than total dissolved Cd2+. These electrochemically inert species may be multinuclear Cd-sulfide clusters and/ or nanoparticles with K(THERM) values that exceed the detection window of pseudopolarography (log K(THERM) > 34.4).

Full Text

Duke Authors

Cited Authors

  • Tsang, JJ; Rozan, TF; Hsu-Kim, H; Mullaugh, KM; Luther, GW

Published Date

  • September 2006

Published In

Volume / Issue

  • 40 / 17

Start / End Page

  • 5388 - 5394

PubMed ID

  • 16999115

Pubmed Central ID

  • 16999115

Electronic International Standard Serial Number (EISSN)

  • 1520-5851

International Standard Serial Number (ISSN)

  • 0013-936X

Digital Object Identifier (DOI)

  • 10.1021/es0525509


  • eng