Copper Ion Selective Membrane Electrode Based on Bis(salphenH₂) Derivatives

New lipophilic bis(salphenH₂) derivative, N,N,N′N″-tetrakis-(3,5-di-tert-butylsalicylidene)-3,3′,4,4′-biphenylene tetramine, L ¹, has been synthesized and tested as an ionophore for copper(II) ion in poly(vinyl chloride) (PVC) membrane electrodes. The combination of this ditopic receptor, L ¹, with dioctylsebacate (DOS) as a plasticizer particularly shows a super-Nernstian slope 36.1 mV/decade of Cu(II) and a detection limit of 2.0 × 10⁻⁶ M is well observed in the pH range from 2.6–4.2 with a response time less than 30 s. The employed ionophore was confirmed to form well-defined stable 2:1 complex with Cu(II) by UV-Vis spectrophotometry. The potentiometric selectivity coefficients determined by matched potential method (MPM) indicate high selectivity for a copper ion in presence of other interfering cations. The proposed electrode offered practically good end-points when the sensor was used as an indicator electrode in the potentiometric titration of copper ions with EDTA.