Determination of Ag(I), Hg(II), Cu(II), Pb(II), Cd(II) by stripping voltammetry in aqueous solutions using complexing polymers in conjunction with membrane filtration

The electrochemical behavior of a series of metal ions (Ag(I), Hg(II), Cu(I I), Pb(II), Cd(II)) and the ternary Cu(II)-Pb(II)-Cd(II) system in the solu tions of water-soluble complexing polymers poly(ethylenimine) (PEI), poly(1 -vinyl-2-pyrrolidone) (PVP), their thiourea-containing derivatives poly(eth yleneimine)methylthiourea (PEI-TU) and poly(1-vinil-2-pyrrolidone) methylth iourea (PVP-TU) was investigated using cyclic and anodic stripping voltamme try (ASV) at different carbon electrodes. The optimum conditions were selec ted for the stripping voltammetric determination of Ag(I), Hg(II), Cu(II), Pb(II) and Cd(II) in a concentration range from 10(-6) to 10(-5) M in the p resence of water-soluble polymers at the carbon-paste electrode (the relati ve standard deviation did not exceed 10%). The stability of metal complexes with PEI was established to decrease in the following order: Hg(II)) > Cu( II) > Ag(I) > Cd(II) > Pb(II). The hydrophilic polymer PEI is shown to redu ce the intermetallic interactions of components of the Cu(II)-Pb(II)-Cd(II) ternary system on the electrode surface. The different complex stabilities of Pb(II), Cd(II) and Cu(II) with PEI allow to determine Pb(II) and Cd(II) in the presence of a larger excesses of Cu(II) (100/1 and 10/1, respective ly) compared to a procedure without PEI (10/1 and 0.33/1, respectively). The conditions were optimized for the simultaneous stripping voltammetric d etermination of the components of the divalent Pb(II)-Cu(II)-Cd(II) system in 2% aqueous solutions of PEI. Finally, the possibility of determining Cu( II) and Pb(II) in tap water after preconcentration as PEI complexes using m embrane filtration was demonstrated. (C)2000 Elsevier Science B.V. All righ ts reserved.