Polarographic Determination of Pb(II) and Cd(II) with Selective Removal of Se(IV) Using Ionic Poly(<Emphasis Type="Italic">N,N</Emphasis>-dimethylacrylamide-co-allylthiourea)

Hydrogels based on N,N-dimethylacrylamide (DMAAm), allylthiourea (ATU), and maleic acid (MA) were synthesized by free-radical cross-linking copolymerization in water with N,N-methylene-bis(acrylamide) (BAAm) as the cross-linker, ammonium persulfate (APS) as the initiator, and N,N,N′,N′-tetramethylenediamine (TEMED) as the activator. Since Se(IV) is the most serious interfering element in the electroanalytical (polarographic or voltammetric) determination of lead and cadmium, a new method for their correct determination after selective separation of the interfering ion (selenite) was developed by using poly(N,N-dimethylacrylamide-co-allylthiourea) P(DMAAm-co-ATU)] hydrogels containing reducing pedant groups like allylthiourea. The proposed method showed good reproducibility and accuracy with relative standard deviations of 8.5 and 3.4% and relative errors of ?6.0 and ?5.4% for the determination of 5.0 × 10^?5 M Pb(II) and Cd(II), respectively, next to 3.0 × 10^?5 M Se(IV).