Iodide buffer systems for the calibration of iodide-selective electrodes

A new approach to the creation of anion buffer systems is proposed, which extends the linear range. The new iodide buffer systems, containing (1) HgI2 precipitate, CaEDTA2−, Ca2+, HgEDTA2−, and (2) HgI2 precipitate, chloride complexes of Hg2+ and excess of Cl− ions, are proposed for the calibration of iodide-selective electrodes at pI > 5. It is shown with the help of these buffers, that a solid-state Orion 94-53 iodide-selective electrode keeps linear Nernstian response up to pI = 7.5. Iodide buffer systems are used for the estimation of the reliability of literature data on selectivity coefficients of iodide-selective electrodes with respect to Cl− ions.