PVC membrane lithium-selective electrodes based on oligomethylene-bridged bis-1,10-phenanthroline derivatives

Poly(vinyl chloride) (PVC) membrane electrodes are prepared for lithium, based on several kinds of synthesized oligomethylene bridged bis-1,10-phenanthroline derivatives as neutral carriers. Potassium tetrakis(p-chlorophenyl)borate (KTCPB) and tetrakis(p-fluorophenyl)borate (TFPB) as lipophilic salts were added into the membranes to improve the selectivity for lithium over alkali and alkaline earth metal ions. The effects of different plasticizers on the electrode performance are discussed. The relationship between the impedance of electrodes and their performance are analyzed, and the membrane composition of the electrode was optimized. The electrode with the optimal membrane composition showed a logKLi,NaPot value of −3.2 (1700 times more selective to lithium ion over sodium ion).