A highly selective thallium(I) electrode based on a thia substituted macrocyclic ionophore.
A new highly Tl(I)-selective PVC membrane electrode based on tetrathia macrocycle 6,7: 14,15-dibenzo-5,8,13,16-tetraoxo-1,4,9,12-tetrathiacyclohexadecane [Bz(2)O(4)(16)aneS(4)] (I) as membrane carrier, o-nitrophenyloctyl ether (o-NPOE) as solvent mediator and potassium tetrakis(p-chlorophenyl)borate (KTpClPB) as lipophilic additive has been developed. The best performance was given by the membrane of macrocycle (I) with composition 3:120:1.5:50 (I:o-NPOE:KTpClPB:PVC). This electrode exhibits a Nernstian response to Tl(I) ions in the concentration range 1.0x10(-1)-2.23x10(-6)M with a slope of 58.2mV/decade of concentration and a detection limit of 1.58x10(-6)M. The response time of the sensor is 12s and can be used over a period of 4 months with good reproducibility. The proposed electrode revealed good selectivity over a wide variety of other cations including alkali, alkaline earth, heavy and transition metals. The electrode works well over a pH range of 3.2-11.5 and in partially non-aqueous medium with up to 30% organic content. The sensor was also used as an indicator electrode in potentiometric titration of Tl(I) ions with KI solution.
Singh
Ashok Kumar
AK
Department of Chemistry, Indian Institute of Technology-Roorkee, Roorkee-247667, India.
Saxena
Puja
P