A palladium imprinted polymer for highly selective and sensitive electrochemical determination of ultra-trace of palladium ions

We report on the design of a palladium(II)-selective electrode based on the use of palladium(II) imprinted polymer nanoparticles (IP-NPs), and its application for the anodic stripping deferential pulse voltammetry determination of palladium ions. The IP-NPs were obtained by precipitation polymerization of 4-vinylpyridine (the functional monomer), ethylene glycol dimethacrylate (the cross-linker), 2,2'-azobisisobutyronitrile (the initiator), eriochrome cyanine R (the palladium-binding ligand), and palladium ions (the template ion) in methanol solution. After polymerization, the Pd2+ in the polymer nanoparticles were leached out with dilute hydrochloric acid to create cavities for hosting Pd2+. The new sensor showed high selectivity for palladium ions in the presence of common potential interferences according to the specific recognition nature of the synthesized imprinted material. A carbon paste electrode was modified with the IP-NPs, and differential pulse stripping voltammetry was applied as the detection technique after open-circuit sorption of Pd2+ ions and its reduction to the metallic form. An explicit difference in the response was observed between the electrodes modified with IP-NPs and electrodes modified with non-IP-NPs. The modified electrode responses to Pd2+ was linear in the 0.01 nmol dm−3 to 1.0 nmol dm−3 (with sensitivity of 92.25 nA/nmol dm−3) and in the 1.0 nmol dm−3 to 1.0 μmol dm−3 (with sensitivity of 16.12 μA/μmol dm−3) concentration ranges. The limit of detection (LOD) of the sensor was 3.0 pmol dm−3 (at S/N = 3). The sensor was successfully applied to the trace determination of Pd2+ in spiked environmental water and soil samples.