SILVER-SELECTIVE MEMBRANE ELECTRODES USING 2-MERCAPTOBENZIMIDAZOLE AND 2-MERCAPTOBENZOTHIAZOLE CARRIERS

ABSTRACT

Silver ion-selective electrodes based on 2-mercaptobenzimidazole (MBI) and 2-mercaptobenzothiazole (MBT) carriers have been developed. The poly(vinyl chloride) (PVC)-based membranes containing MBI or MBT, plasticizer and sodium tetraphenylborate, as anion excluder and membrane modifier, were directly coated on the surface of graphite electrodes. The electrodes exhibited near-Nernstian slopes of 60.2 and 57.8 mV per decade of Ag⁺ concentration for MBI and MBT, respectively. Calibration plots were linear over a wide concentration range of 1 × 10⁻⁶–1 × 10⁻² M Ag⁺. The electrodes have shown detection limits of 6.3 × 10⁻⁷ and 4 × 10⁻⁷ M for MBI- and MBT-based electrodes, respectively, and revealed good selectivities over a number of alkali, alkaline earth, transition and heavy metal ions. The electrodes have response times between 10–20 s and can be used for at least two months without a considerable divergence in their potential responses Application of the electrodes for potentiometric titrations and determination of Ag⁺ ion concentration in photographic waste solutions are reported.

Keywords:

• Silver-selective electrode
• Sensors
• Coated-graphite electrode
• Potentiometric sensors
• 2-Mercaptobenzimidazole
• 2-Mercaptobenzothiazole
• Ion-selective electrode

ACKNOWLEDGMENTS

The authors express their appreciation to the University of Isfahan Research Council for financial support of this work.