PSEUDO-POLAROGRAPHIC DETERMINATION OF METAL-COMPLEX STABILITY-CONSTANTS IN DILUTE-SOLUTION BY RAPID SCAN ANODIC-STRIPPING VOLTAMMETRY

The theory of anodic stripping voltammetry states that at any deposition potential, the deposition current will either be the limiting current or a fraction of the limiting current, depending on the deposition potential with respect to the metal deposition potential. By using a computer controlled anodic stripping voltammeter with automatic background correction, pseudopolarograms can be obtained by plotting the peak area vs. the deposition potential for a series of stripping voltammetric runs. With ASV as a method of amplification, the ligand number and stability constants are determined for metal complexes at concentration ranges expected of natural water systems. Results for lead and cadmium with chloride and carbonate are In excellent agreement with those of less sensitive methods used at higher concentrations. No complexatlon of lead and cadmium was found with glycine at pH 4.68. The structure of arsenic(III) at 1.0 ng/mL in acidic solutions was determined to be As(OH)3 using a gold film electrode. Finally, the speclatlon of lead In a geothermal water was examined by pseudopolarography and a shift consistent with a PbCI+ complex was observed. © 1979, American Chemical Society. All rights reserved.