Affiliation: Department of Chemical Technology, LPQA/LAPQAP-UFMA, São Luis, MA, Brazil.
An improved procedure is presented to determine Pb(II) and Cu(II) in gasoline using a mercury film electrode generated in situ. The method is based on the reduction of the metal ions at adequate potentials on the glassy carbon electrode, in whose optimized microemulsion medium composition, the ions can be determined directly and simultaneously by differential pulse anodic stripping voltammetry. Good results were obtained in terms of analytical performance and voltammetric wave forms, with two stripping peaks near to -0.420 V and -0.13 V, attributed to Pb(II) and Cu(II), respectively. Linear responses for both metal ions indicated quite low detection limits (2.1x 10-9 mol L-1 for Pb(II) and 2.4 x 10-9 mol L-1 for Cu(II)). The method was applied successfully to real gasoline samples, presenting good results for precision (variation coefficients of 12.4% and 10.2%) and accuracy (recoveries ranging from 96.7 to 99.33% and 101.33 to 102.67%), for Pb(II) and Cu(II), respectively.