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 Original Research Article

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).