119 J. Elecrroanal. zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Chem., 344 (19931 119-134 Elsevier Sequoia S.A., Lausanne JEC 02329 Polarography and differential pulse anodic stripping voltammetry of Pb( II) /polycarboxylate complexes Jose M. Diaz-Cruz, Cristina Arifio, Miquel Esteban l and Enric Casassas Department of Analytical Chemistry, University of Barcelona, AL.. Diagonal 647, 08028 Barcelona (Spain) Herman P. van Leeuwen Laboratory for Physical and Colloid Chemistry, W ageningen Agricultural Unicersity, Dreijenplein 6, 6703 HB W ageningen (Netherlands) (Received 3 February 19921 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Abstract Complex formation of Pb(lI) with polymethacrylic acid (PMA) and polyacrylic acid (PAA) is studied by sampled direct current, normal pulse, reverse pulse, and differential pulse polarography, by cyclic voltammetry and by differential pulse anodic stripping voltammetty. The two PMII) systems appear to be labile on the different time scales of several techniques, and at different ligand-to-metal ratios. Voltammetric titrations of PM111 with partially neutralized PMA or PAA allow the precise determina- tion of the apparent formation constants K of the complexes present in both systems. Under conditions where adsorption of PM111 onto the cell walls is not negligible, i.e. at low concentrations and at pH > 4.5, the application of a previously described methodology also allows the precise determination of K by introducing a correction due to adsorption. In some cases anomalous behaviour is still observed, which cannot be explained by adsorption losses. INTRODUCTION The interactions between homofunctional synthetic polyacids such as polyacrylic acid (PAA) and polymethacrylic acid (PMA), with fairly sharp molar mass distribu- tions, and several metal ions have been widely studied by voltammetric techniques [l]. For some of the properties of natural polyelectrolytes, these polyacids are satisfactory model compounds that have been used widely in the interpretation of speciation studies of metal ions in natural waters [2]. l To whom correspondence should be addressed. 0022-0728/93/$06.00 0 1993 - Elsevier Sequoia S.A. All rights reserved