PVC membrane sensor for potentiometric determination of iron (II) in some pharmaceutical formulations based on a new neutral ionophore

A novel poly (vinyl chloride) PVC membrane sensor for Fe²⁺ ions is described. The sensor is based on the use of newly synthesized chiral 2,6‐bis‐(carboxamide methyl ester)pyridine derivative as neutral ionophore in plasticized PVC membrane. The sensor display a fast, stable and near‐Nernstian response over a relative wide ferrous concentration range (1 × 10^?3 to 6 × 10^?6 M), with cationic slope of 31.5 ± 0.5, mV per concentration decade over a pH range of 5.0–9.0. The direct determination of 0.25–56.0 µg/ml of ferrous in aqueous solution shows an average recovery of 98.5% and a mean relative standard deviation of 1.5% at 20.0 µg/ml. The sensor displays long life‐span, long‐term stability, high reproducibility, and short response time. Selectivity coefficients for Fe(II) relative to a number of interfering substances were investigated. The sensor shows high significantly for Fe²⁺ over Fe,³⁺ Cu,²⁺ Zn,²⁺ Cd,²⁺ Hg,²⁺ Pb,²⁺ Ni,²⁺ Co,²⁺ Mn,²⁺ Al,³⁺ alkaline earth and alkali metal ions. The sensor is successfully applied for measurement of ferrous in drug formulations. The results obtained for the determination of ferrous using the proposed sensor are comparable favourably with those obtained using the spectrophotometric method. Copyright © 2010 John Wiley & Sons, Ltd.