Resumo:
Controlled adsorptive accumulation of copper complexed with TAN, TAC, TAR and TAM (heterocyclic azo-compounds) on a static mercury drop electrode provides the basis for the direct stripping measurement of this element in the nanomolar concentration level. The ligand TAN exhibited great sensitivity and better separation of the peak current of the ligand in relation to the complex. The reduction current of adsorbed complex ions of copper is measured by linear scan cathodic stripping voltammetry, preceded by a period of accumulation of a few minutes. The peak potential is at ∼ −0.37 V vs. Ag/AgCl. Optimal experimental parameters were found to be a TAN concentration of 1 × 10−5M, an accumulation potential of −0.22 V, and a solution pH of 3.7 (acetate buffer). The detection limit is 0.8nM after a 5-min accumulation with a stirred solution, and the response is linear up to 50 μg/l. Many common cations and anions do not interfere in the determination of copper. The interference of titanium is eliminated by addition of fluoride ion. Results are reported for a fresh water sample.
