ISSN:
1040-0397
Keywords:
Zinc
;
Complexation
;
Seawater
;
Rainwater
;
Pseudopolarogram
;
Trace metal
;
Voltammetry
;
Square wave anodic stripping voltammetry
;
Complexometric titration
;
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
A novel electrochemical method is described for the examination of metal-organic complexation in natural waters. The technique is based upon the comparison of square wave anodic stripping voltammetry (SWASV) ‘pseudopolarograms’ (current vs. deposition potential plots) for natural samples with those obtained for metal complexation with selected ‘model’ binding ligands at constant ionic strength. For electrochemically active zinc species in seawater, the pseudopolarogram approach allowed the estimation of thermodynamic stability constants (KML) within a stability constant window of approximately 104-106 M-1 up to ≥ 1015 M-1. For a natural rainwater sample, the pseudopolarogram indicated only one zinc class, probably a mixture of ‘free’ and/or inorganically complexed species. In an application to a coastal seawater sample, three species were identified: (1) weakly complexed, log KZnL = 4.14 ± 0.92 M-1; (2) moderately complexed, log KZnL = 7.77 ± 0.62 M-1; (3) strongly complexed, log KZnL = 11.45 ± 0.95 M-1. Results are compared to those obtained using complexometric titration with SWASV at a thin mercury film-glassy carbon rotating disk (TMF-GCRD) electrode. The latter detected a single strong complexing ligand (or ligand class), with [L′] = 15.25 ± 0.04 nM and log K′ZnL ≥ 10.9 M-1.
Additional Material:
13 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/elan.1140070213
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