This study concerns the evaluation of ionophoric properties of a functionalized calix 10 −7 -1 × 10 −3 M of erbium ions, with a limit of detection of 3.8 × 10 −8 M. Its potential response was independent of pH variation in the relatively wide range 4.5-6.5. The dynamic response time of the electrode to achieve a steady potential was found to be about 7 s. The selectivity of the sensor towards erbium ions with respect to several mono-, di-, tri-, and tetravalent metal ions was examined. The prepared sensor can be used for 3 months without considerable divergences in potential response. The performance of the sensor was examined as an indicator electrode for complexometric titration of erbium solutions by EDTA
