COMPARISON BETWEEN POLAROGRAPHIC AND POTENTIOMETRIC SPECIATION FOR CADMIUM HUMIC ACID SYSTEMS/

Potentiometric and polarographic metal speciation results were compare d for a cadmium/humic acid complex system. Three polarographic techniq ues were used: normal (NPP), differential (DPP) and reverse (RPP) puls e polarography. Satisfactory agreement between potentiometric and pola rographic data is obtained for systems with pH below 5. RPP generally shows better agreement than NPP and DPP. The discussion of the results includes lability, effects of heterogeneity and adsorption of humic a cids at the mercury electrode.