ADDITIONAL EVIDENCE OF THE OPERATIONAL CHARACTER OF THE LABILITY OF COMPLEXES OF COPPER(II) WITH SIMPLE ORGANIC-LIGANDS

A fixed analytical window of observation, 5 mu mol l(-1) free copper a nd 100 mu mol l(-1) total copper, but methods different in nature, ope ration mode and time scale were applied, in parallel, at pH 6.50 and 1 6 degrees C, to solutions with copper complexes of very different ther modynamic stabilities. Ethylenediaminetetraacetic acid (EDTA), L-cyste ine, L-lysine, L-proline and succinate were used as metal buffers. Chi tin (batch and column modes), chelex-100 (column mode) and normal puls e anodic stripping voltammetry (NPASV, -0.3 V deposition potential) we re used as techniques. A strategy, based on using the mass of polymer that provided uptake of free copper similar to that taken up by Pseudo monas syringae bacterial cells in absence of ligands, was used for all but NPASV methods. Flame atomic absorption spectrophotometry was used for metal detection. The lability of copper complexes with simple org anic ligands showed a strongly operational character. The time scale o f the physicochemical method used for the determination of lability wa s not the only parameter inherent to the method that influenced the ex tent of copper complex dissociation. The nature of both initial and co mpeting ligands and the operation mode may also condition the speciati on results.