IODIDE BUFFER SYSTEMS FOR THE CALIBRATION OF IODIDE-SELECTIVE ELECTRODES

A new approach to the creation of anion buffer systems is proposed, wh ich extends the linear range. The new iodide buffer systems, containin g (1) HgI2 precipitate, CaEDTA(2-), Ca2+, HgEDTA(2-), and (2) HgI2 pre cipitate, chloride complexes of Hg2+ and excess of Cl- ions, are propo sed for the calibration of iodide-selective electrodes at pI > 5. It i s shown with the help of these buffers, that a solid-state Orion 94-53 iodide-selective electrode keeps linear Nemstian response up to pI = 7.5. Iodide buffer systems are used for the estimation of the reliabil ity of literature data on selectivity coefficients of iodide-selective electrodes with respect to Cl- ions.