Bifunctional Ion‐Selective Electrode Based on C60‐Cryptand 22 for Silver and Iodine Ions

Abstract

AbstractFullerence C60‐cryptand 22 was prepared and successfully applied as the electric carrier in the PVC electrode membrane of a bifunctional ion‐selective electrode for cations, e.g., Ag+ ions as well as anions, e.g., I− ions. The bifunctional ion‐selective electrode based on C60‐cryptand 22 can be applied as a Silver (Ag+) ion selective electrode with an internal electrode solution of 10−3 M AgNO3 in water (pH = 6.3), or as an Iodide (I−) ion selective electrode with an acidic internal electrode solution of 10−4 M KI(aq) (pH = 2) in which the cryptand 22 is protonated, and the C60‐cryptand 22 is changed to C60‐Cryptand22–H+ and becomes an anionic electro‐carrier to absorb the I− ion. The Ag+ ion selective electrode based on C60‐cryptand 22 gave a linear response with a near‐Nernstian slope (59.5 mV decade−1) within the concentration range 10−1‐10−3 M Ag+(aq). The Ag+ ion electrode exhibited comparatively good selectivity for silver ions, over other transition‐metal ions, alkali and alkaline earth metal ions. The Ag+ ion selective electrode with good stability and reproducibility was successfully used for the titration of Ag+(aq) with Cl− ions. The Iodide (I−) Ion selective electrode based on protonated C60–cryptand22‐H+ also showed a linear response with a nearly Nernstian slope (58.5 mV decade−1) within 10−1 ‐ 10−3 M I− (aq) and exhibited good selectivity for I− ions and had small selectivity coefficients (10−2–10−3) for most of other anions, e.g., F− , OH−, CH3COO−, SO42−, CO32−, CrO42−, Cr2O72− and PO43− ions.