Highly selective potentiometric determination of mercury(II) ions using 1-furan-2-yl-4-(4-nitrophenyl)-2-phenyl-5H-imidazole-3-oxide based membrane electrodes.

The electrode characteristics and selectivities of PVC-based mercury(II) selective coated graphite electrode (CGE) and polymeric membrane electrode (PME) incorporating the recently synthesized 1-furan-2-yl-4-(4-nitrophenyl)-2-phenyl-5H-imidazole-3-oxide are reported here. The electrodes exhibit Nernstian slope for mercury(II) ions over wide concentration ranges, i.e. 1.0 x 10(-1)M to 1.0 x 10(-6)M (with CGE) and 1.0 x 10(-1)M to 1.0 x 10(-5)M (with PME). The lower detection limits shown by CGE and PME are 8.91 x 10(-7)M and 6.30 x 10(-6)M, respectively, in the pH range of 1.0-4.0. From the comparative study of these electrodes, CGE has been found to be better than PME in terms of lower detection limit and better selectivity for mercury(II) ions with comparatively less interference from silver(I) ions. The proposed electrodes can be successfully used as an indicator electrode for potentiometric titration of mercury with potassium dichromate. The electrodes have been successfully applied for estimation of mercury content in synthetic water samples, insecticide (parad tablet) and dental amalgam.

2,6-bis-methylsulfanyl-[1,3,5]thiadiazine-4-thione as a Ag+-selective ionophore.

A silver ion-selective electrode was prepared with a polymeric membrane incorporating 2,6-bis-methylsulfanyl-[1,3,5]thiadiazine-4-thione as an ionophore, tri-n-butylphosphate (TBP) as a plasticizer and sodium tetraphenylborate (NaTPB) as an additive. The electrode exhibited a near-Nernstian response of 52 mV/decade over a wide linear concentration range of 1.0 x 10(-5) - 1.0 x 10(-1) M with a lower detection limit of 9.77 x 10(-6) M. The electrode exhibited excellent selectivity for silver ion over many of the alkali, alkaline-earth and transition metal ions. The electrode worked well over a wide pH range of 1.77 - 7.13. The response time of the electrode was less than 20 s. The sensor can be applied as indicator electrode for the potentiometric titration of Ag+ ions with Cl- ions.