A new PVC-membrane electrode based on a diazatetrathia (N2S4) macrocyclic ligand for selective determination of silver ion

A poly(vinyl chloride) based membrane based on neutral macrocyclic ionophore: 2,3,4:10,11,12-dipyridine-3,11-diaza-1,5,9,13-tetrathiacyclohexadeca-2,10-diene with sodium tetraphenyl borate (STB) as an anion excluder and dibutylphthalate (DBP) and dioctylphthalate (DOP) as plasticizing solvent mediator was prepared and investigated as a Ag(I)-selective electrode. The best performance was observed with the membrane having the ligand-PVC-DBP-STB composition 1:6:1:2, which worked well over a wide concentration range (3.98 x 10(-6) mol L-1-1.00 x 10(-1) mol L-1) with a Nernstian slope of 55.3 mV per decade of activity between pH 3.0-7.0. This electrode showed a fast response time of 15 s and was used over a period of three months with good reproducibility (S = 0.3 mV). The selectivity coefficient for mono-, di-, and trivalent cations indicate excellent selectivity for Ag(I) ions over a large number of cations. Anions such as NO3- and SO42- do not interfere and the electrode also works satisfactorily in a partially nonaqueous medium. The sensor has been used as an indicator electrode in the potentiometric titration of Ag(I) with Nal solution. It has also been used successfully for determination of Ag(I) in real samples.