Papers Published

1. Tsang, Jeffrey J. and Rozan, Tim F. and Hsu-Kim, Heileen and Mullaugh, Katherine M. and Luther III, George W., Pseudopolarographic determination of Cd²⁺ complexation in freshwater, Environmental Science and Technology, vol. 40 no. 17 (2006), pp. 5388 - 5394 [es0525509] .
   (last updated on 2007/04/09)

   Abstract:
   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 Cd²⁺-organic complexes were detected at each site. These unknown Cd²⁺ complexes were characterized by their half-wave potential (E_1/2). The E _1/2 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 Cd ²⁺ 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). © 2006 American Chemical Society.

   Keywords:
   Water quality;Cadmium;Complexation;Thermodynamic stability;Concentration (process);Nanostructured materials;