Dióxido de chumbo eletrodepositado sobre grafite como sensor potenciométrico a íons chumbo e sulfato

Abstract

The development of a PbO2 electrodeposited in a graphite substrate electrode and evaluation of its potenciometric response as a sensor for Pb2+ and SO42- ions, at constant pH and ionic strength is described. The electrode was applicated in the potenciometric titration in precipitation reaction of Pb2+ with SO42- in hydroethanolic medium. The results showed that the PbO2 electrodeposited electrode is useful as a potenciometric sensor to the Pb(II) ions presenting a linear response range between 3,98∓10-4 a 3.09∓10-2 mol L-1 in nitrate medium, with a practical detection limit of (4,98 ± 0,11)×10-4 mol L-1. For sulphate ions the PbO2 electrode did not responded directly. These ions might be dosed indirectly by potentimetric titration with standard Pb(II) solution in acidic media, in 1:1 ethanol-water (v/v), with good definition of the equivalence volumes. The reprodutibilidade of the potenciais and of the equivalence volumes obtained in samples with concentration at milimolar level in sulphate, indicate the possibility of the use of this electrode in quantifying sulphate ions.