Silver-selective membrane electrodes using 2-mercaptobenzimidazole and 2-mercaptobenzothiazole carriers

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 x 10(-6)-1 x 10(-2) M Ag+. The electrodes have shown detection limits of 6.3 x 10(-7) and 4 x 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.