To predict the selectivity of Yb(III)-PVC membrane, the semiempirical PM6/SPARKLE method was used to investigate the binding of Yb(III) and other cations to 1,10-phenanthroline-5,6-dione (PDO). The study has shown that the chelating ligand, PDO, is selectively coordinated to Yb(III) at two coordination sites involving the pyridylic nitrogen atoms in the interface of membrane/solution. The membrane was used as a potentiometric Yb sensor, based on PDO as an ionophore, sodium tetraphenyl borate (NaTBP) as a lipophilic ionic additive, and tributyl phosphate (TBP) as a plasticizer. The electrode had a good Nernstian response for Yb(III) ions over a wide concentration range from 5 x 10(-6) to 1 x 10(-2) M and a detection limit of 5.7 x 10(-7) M with a slope of 19.7 +/- 0.2 mV/decade in a pH range of 4.0-12.0. The sensor had a very fast response time of less than 5 s over the whole concentration range and can be used over a period of 6 wk without any significant divergence in potentials. (C) 2010 Elsevier Inc. All rights reserved.