Preparation of a Lead Ion-Selective Electrode Based Upon Crown Ether Nitrobenzo18-Crown-6

Nitrobenzo18-crown-6 (NB18C6) 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 30% PVC, 58.5% ortho-nitrophenyloctylether (NPOE) as plasticizing solvent mediator, 9% of NB18C6 as ionophore and 2.5% sodium tetraphenylborate (NaTPB) as ion excluder. The electrode presents a nearly Nernstian response (a slope of 30.5±0.5 mV/decade) over a concentration range 1×10-5-1×10-2 M of lead ions, with a limit of detection 8.9×10-6 M. Its potential response was independent on the pH variation in the range 2.2-4.1. The dynamic response time of the electrode to achieve a steady potential was relatively fast and was found to be about 6 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 3 months without considerable divergences in the potential response. It was successfully used as an indicator electrode for the complex formation titration of lead solutions by EDTA.