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(II), Pb(II), Cd(II)) and the ternary Cu(II)-Pb(II)-Cd(II) system in the solutions of water-soluble complexing polymers poly(ethylenimine) (PEI), poly(1-vinyl-2-pyrrolidone) (PVP), their thiourea-containing derivatives poly(ethyleneimine)methylthiourea (PEI-TU) and poly(1-vinil-2-pyrrolidone) methylthiourea (PVP-TU) was investigated using cyclic and anodic stripping voltammetry (ASV) at different carbon electrodes. The optimum conditions were selected 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 presence of water-soluble polymers at the carbon-paste electrode (the relative 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 reduce 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, respectively) compared to a procedure without PEI (10/1 and 0.33/1, respectively). The conditions were optimized for the simultaneous stripping voltammetric determination 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 membrane filtration was demonstrated. (C)2000 Elsevier Science B.V. All rights reserved.