In this work a dysprosium [Dy(III)]-selective solvent polymeric membrane sensor based on N,N-bis(pyrrolidene) benzne-1,2-diamine, poly(vinyl chloride)(PVC), the plasticizer benzylacetate (BA), and anionic site is described. This sensor responds to Dy(III) activity in a linear range from 1.0 Â 10 À5 to 1.0 Â 10 À1 M, with a slope of 20.6 AE 0.2 mV per decade and a detection limit of 6.0 Â 10 À6 M at the pH range of 3.5 -8.0. It has a fast response time of < 20 s in the entire concentration range, and can be used for at least 2 months without any considerable divergence in the electrode potentials. The proposed sensor revealed comparatively good selectivity with respect to common alkali, alkaline earth, transition and heavy metal ions. It was used as an indicator electrode in the potentiometric titration of fluoride ions and in determination of concentration of F -ions in some mouth washing solutions.

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