Abstract: This paper describes the selectivities of a PVCmembrane based on tetra-phenylborate (NaTPBor KTPB) containing dioctyl phenylphosphonate (DOPP) or tributylphosphate (TBP) as mediator solvent for metal ions. The results obtained showed that a lithium ion-selective electrode based on KTPBwith DOPPas. mediator solvent is better, giving linear response in the activity range of 5×10^-5-10^-1mol/LLi⁺ and detection limit of 6.5×10^-6mol/LLi⁺. Selectivity coefficients are as follows: The performances of the electrode were compared with those of typical lithium selective electrodes reported recently. This electrode is an useful sensor for lithium.

Key words: Li⁺ Ion-selective electrode, Mediator solvent, Sodium tetraphenylborate, Potassium tetraphenylborate