Design and Optimization of a PVC Membrane Sensor for Enhanced Selectivity and Sensitivity Towards Co (II) Ions

Narendra Kumar

Cobalt ion-selective electrode, PVC membrane, Potentiometry, Schiff base.

A novel PVC membrane-based potentiometric sensor was designed for the selective detection of Co²⁺ ions, utilizing the Schiff base ligand 3-chloro-N'- (2-hydroxybenzylidene) benzo hydrazide (S-2) as the neutral ionophore. The ionophore’s unique ability to exist in two tautomeric forms—amide and imidol—is pivotal to its high affinity for Co²⁺ ions. The hydroxyl group in the imidol form significantly enhances chelation, making S-2 an effective candidate for cobalt sensing. The sensor exhibits a wide linear detection range from 1.0 × 10^-1 to 1.0 × 10^-¹ mol L^-1, with an impressive detection limit of 4.0 × 10^-7 mol L^-1. It demonstrates near-Nernstian sensitivity, characterized by a slope of 29.7 mV per decade. The electrode delivers a rapid response time of approximately 10 seconds and remains stable for up to 12 weeks without significant performance degradation. High selectivity for Co²⁺ was observed, even in the presence of commonly interfering cations, and the sensor maintains optimal functionality across a pH range of 5.0 to 12.0. The practical performance of the sensor was validated through its application in potentiometric titrations of Co²⁺ with EDTA and the direct determination of cobalt concentrations in environmental samples. This study underscores the potential of the developed sensor for accurate and reliable cobalt ion detection, with broad applications in environmental analysis and industrial monitoring.