Surface modification by 8-hydroxyquinoline-5-sulfonic acid (8-HQS) or 8-hydroxyquinoline (8-HQ) on a graphite electrode through irreversible adsorption is reported in this paper. Cyclic voltammetry was used to characterize the surface behavior. The modified surface exhibited an affinity to chelating Cu(II) in the solution, forming a Cu(II) complex, which was employed for Cu(II) trace analysis. Of the metals Zn, Ni, Pb, Co, and Cd, none presented interference until excess concentration of 10 times. Significant interference could be observed from Co(II), Cd(II) and Fe(II) for an excess concentration of 100 times on the analyte. A differential pulse voltammetry, combined with a preconcentrating-stripping process and a standard addition method was used for the analysis. A detection limit for trace copper determination in water, such as 5.1<FONT FACE=Symbol>´</FONT>10-9 mol L-1, was obtained.
8-hydroxyquinoline-5-sulfonic acid; 8-hydroxyquinoline; surface complex; stripping voltammetry; trace copper determination
