Benzo15-crown-5 as Sensory Molecule for Fabrication of a Lead(II) Ion-selective Potentiometric Sensor

Benzo15-crown-5 (B15C5) has been examined as an ion sensing material for fabricating a PVC membrane lead ion-selective potentiometric sensor. The best performance of the electrode was observed with a membrane composition formed by 29% PVC, 60% dibutylphthalate (DBP) as plasticizing solvent mediator, 2% sodium tetraphenylborate (NaTPB) as ion excluder and 9% of B15C5 as ionophore. The electrode presents a nearly Nernstian response (a slope of 29.7 +/- 0.5 mV/decade) over a concentration range 1x10(-5)-1x10(-3) M of lead ions, with a limit of detection 8.4x10(-6) M. Its potential response was independent on pH variation in the range 2.8-4.5. The dynamic response time of the electrode to achieve a steady potential was found to be about 25 seconds. The selectivity of the prepared electrode relative to some mono-, di-, tri- and tetra-valent metal ions was examined. This electrode can be used for 2 months without considerable divergences in the potential response. It was successfully used as an indicator electrode for the complex formation titration of lead inwater sampless by EDTA.