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

A new PVC membrane electrode for Co2+ ions based on (2-mercapto-4-methylphenyl)-2-benzamido-3-phenyl-thiopropenoate (1) as an excellent neutral carrier was prepared. The electrode exhibits a Nernstian response for Co2+ ions over a wide concentration range (1.0 x 10(-2) to 4.0 x 10(-7) M) with a slope of 30 +/- 1 mV per decade. The limit of detection is 1.0 X 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. (C) 2002 Elsevier Science B.V. All rights reserved.