Coated Wire Ion Selective Electrode Based on a New Crown Ether for Determination of ${\rm Fe}^{2+}$

A coated wire Fe²⁺ ion selective electrode based on laboratory-synthesized crown ether, as a neutral carrier, was constructed. The effects of different experimental parameters such as the amount of plasticizer, the amount of ionophore, pH of the sample solution, and coexisting ions on the potentiometric responses of the electrode were investigated. The electrode exhibited a Nernstian slope of 29.20±0.87 mV/decade over a wide concentration range of 7.2×10^-7-6.9×10^-3 M Fe²⁺. The potentiometric responses were independent of the pH of the test solution in the pH range of 4.6-9.6. The response time and detection limit were found to be 3.0 min and 6.7×10^-7 M, respectively. The electrode revealed good selectivity for Fe²⁺ in the presence of different coexisting cations and anions. It was certified as an indicator electrode by performing a potentiometric titration for a standard sample of Fe²⁺ ion.