Cobalt(II)-selective membrane electrode using a recently synthesized mercapto compound Original Research Article

A new PVC membrane electrode for Co2+ ions based on (2-mercapto-4-methylphenyl)-2-benzamido-3-phenyl-thiopropenoate (I) as an excellent neutral carrier was prepared. The electrode exhibits a Nernstian response for Co2+ ions over a wide concentration range (1.0×10−2 to 4.0×10−7 M) with a slope of 30±1 mV per decade. The limit of detection is 1.0×10−7 M (0.006 ppm). It has a fast response time of <5 s and very high lifetime as can be used for at least 6 months without any divergence in potential. The proposed sensor revealed good selectivities over a wide variety of other cations including alkali, alkaline earth, heavy and transition metals and could be used in the pH range 5.0–8.0. This electrode was successfully applied for the direct determination of Co2+ in solution and, as an indicator electrode, in potentiometric titration of cobalt ions.