PVC membrane and coated graphite potentiometric sensors based on 1-phenyl-3-pyridin-2-yl-thiourea for selective determination of iron(III)

The construction and performance characteristics of PVC membrane (PME) and coated graphite (CGE) Fe3+ ion selective electrodes based on 1-phenyl-3-pyridin-2-yl-thiourea (PPT) are described. The electrodes exhibit a Nernstian slope of 20.2 ± 0.8 (CGE) and 19.9 ± 0.4 (PME) mV decade−1 of activity in Fe3+ ion over a wide concentration range from 3.0 × 10−7 to 1.0 × 10−2 M for CGE and 6.9 × 10−7 to 1.0 × 10−2 M Fe3+ for PME. The lower detection limits by CGE and PME are 2.0 × 10−7 and 3.9 × 10−7 M, respectively, in the pH range of 1.8–5.6 for PME and 1.8–5.8 for CGE with a fast response time (<10 s). The standard electrode potentials were determined at different temperatures and used to calculate the isothermal coefficient of the PME. The PME showed the working temperature range of 22–55 °C with isothermal temperature coefficient of 1.33 × 10−3 V/°C and it was also used in non-aqueous solvents. The electrodes were successfully applied to determine iron(III) in water samples.