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

Fullerence 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 AgNO 3 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 − , CH 3 COO − , SO 4 2− , CO 3 2− , CrO 4 2− , Cr 2 O 7 2− and PO 4 3− ions.