RESUMO
Square-wave (SW) voltammetry in connection with a hanging mercury drop electrode has been applied for studying the reduction of Ge(IV) catalyzed by o-catechol after adsorptive preconcentration. Acetate buffer solutions with low and high analytical concentrations of o-catechol [with respect to that of Ge(IV)] have been used. Dependences of SW catalytic peaks on accumulation conditions have been attributed to the formation of the catalytic complexes via a direct-adsorption mechanism. The nature of the electrocatalytic process (involving an apparently quasi-reversible electrode reaction with an adsorbed reactant and a diffusing product) allows us to explain complex dependences of catalytic peaks on SW-parameters. Adequate conditions for determination of o-catechol and Ge(IV) by means of SW catalytic adsorptive voltammetry have been established.
RESUMO
The reduction at mercury electrodes of a new 5-nitrofuran derivative with antibacterial activity, N2-(5-nitrofurfurylidene)formohydrazide-4-(3,5-dicyanophenyl)-6-ethoxy-2- pyridyl)imide, was studied by conventional, normal pulse, reverse normal pulse and differential pulse polarography in water-dimethylformamide (30%) buffered media. The waves observed, whose number depended on pH, are attributed to the reduction of the nitro group (6 electrons) and the azomethinic unit (4 electrons). The basic mechanisms of the electrode reactions have been deduced from the characteristics of the waves. Conditions for determining the formal potential of the nitroderivative/radical-anion system, a parameter related to pharmacological activity, are also reported.
