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A europium selective PVC membrane sensor based on 4-methylphenylisothiocyanate (4-MePIC) as a suitable neutral ionophore is introduced. The semiempirical PM6/SPARKLE calculations were performed to investigate the interaction between the 4-MePIC ligand, Eu(III) and interfering cations. The obtained results were used to predict the selectivity of the proposed sensor. The standard enthalpy of reaction (ΔHr°) has been used to predict the selectivity of the 4-MePIC ligand to a particular cation, except when the complex formation was controlled by the kinetic parameters. The computational data have been shown that the 4-MePIC ligand could be used as a suitable neutral ionophore in fabrication of a Eu(III) ion selective electrode. The nephelauxetic parameter (β) indicates a significant covalent character in the Eu(III)- ionophore complex. The proposed sensor has a very fast response time with a near Nernstian response of 19.7 ± 0.3 mV decade-1 for Eu(III) over a concentration range from 1 × 10-6 to 1 × 10-2 M with a detection limit of 1 × 10-6 M. It was applied for Eu(III) determination in various synthetic and mouthwash samples with satisfactory results.