Mercury(II) and silver(I) ion-selective electrodes based on dithia crown ethers

Abstract

Mercury (Hg²⁺) and silver (Ag⁺) ion-selective PVC membrane electrodes based on 1,4-dithia-12-crown-4 and 1,4-dithia-15-crown-5 as neutral carriers were successfully developed. Both electrodes exhibited good linear responses of 30 and 40 mV decade^–1 for Hg²⁺ and Ag⁺, respectively, within the concentration ranges 10^–2-10^–6M Hg(NO₃)₂ and 10^–1-10^–6M AgNO₃. Some other crown ethers and cryptands were also investigated as neutral carriers for both ions. Both the mercury and silver electrodes exhibited comparatively good selectivities for mercury(II) and silver(I) ions in comparison with alkali metal, alkaline earth metal and some heavy metal ions. These crown ether ion-selective electrodes are suitable for use with aqueous solutions at pH 2. They were applied as sensors in titrations of Br^– and Cl^– with Ag⁺ and of Hg²⁺ with l^– and Cr₂O₇^2– and in the determination of the solubility products of AgCl in aqueous solutions.