New polymeric membrane cadmium(II)-selective electrodes using tripodal amine based ionophores

Fabrication of PVC membrane electrodes incorporating selective neutral carriers for Cd2+ was reported. The ionophores were designed to have different topologies, donor atoms and lipophilicity by attaching tripodal amine (TPA) units to the lipophilic anthracene (ionophore I) and p-tert-butylcalix[4]arene (ionophores II, III and IV). The synthesized ionophores were incorporated to the plasticized PVC membranes to prepare Cd(II) ion selective electrodes (ISEs). The membrane electrodes were optimized by changing types and amounts of ionic sites and plasticizers. The selectivity of the membranes fabricated from the synthesized ionophores was evaluated, the relationship between structures of ionophores and membrane characteristics were explored. The ionophore IV which composed of two opposites TPA units on the calix[4]arene compartment showed the best selectivity toward Cd2+. The best membrane electrode was fabricated from ionophore IV (10.2 mmol kg−1) with KTpClPB (50.1 mol% related to the ionophore) as an ion exchanger incorporated in the DOS plasticized PVC membrane (1:2; PVC:DOS). The Cd-ISE fabricated from ionophore IV exhibited good properties with a Nernstian response of 29.4 ± 0.6 mV decade−1 of activity for Cd2+ ions and a working concentration range of 1.6 × 10−6–1.0 × 10−2 M. The sensor has a fast response time of 10 s and can be used for at least 1 week without any divergence in potential. The electrode can be used in the pH range of 6.0–9.0. The proposed electrodes using ionophores III and IV were employed as a probe for determining Cd2+ from the oxidation of CdS QDs solution and the real treatment waste water sample with excellent results.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► New four ionophores having tripodal amine (TPA) unit on anthracene and calixarene. ► Synthesis and characterization data were reported. ► Incorporated to the plasticized PVC membranes to prepare Cd-ISEs. ► Two TPA units on calixarene showed the best selectivity toward Cd2+. ► Applied for sensing Cd2+ from the oxidation of CdS QDs solution.