Magnesium Ion Selective Electrodes Based on β-Diketone Compounds

The ion selectivities for poly(vinyl chloride) (PVC)-matrix membrane ion-selective electrodes based on seven lipophilic diketone compounds were examined. All the electrodes based on the tested five β-diketone cómpounds exhibited clear Mg 2 ′-selectivity under high pH conditions (pH10). Especially, the electrode based on 2-acetyl-1-tetralone shows excellent Mg 2+ -selectivity, and the selectivity coefficients of the Mg 2 + -electrode to Ca 2 +, K + and K + (log K pot mg, ca log K pol mg.k and log K pot Mg.Na ) in pH 10 solution were −2.2, −1.9 and −2.7, respectively. This elecrode gave a response slope of about 60 mV/pMg 2+ ranging from 1 × 10 −2 to 2 × 10 −2 , which corresponds to twice the usual Nernstian theoretical responce slope for the divalent cation. This phenomenon is advantageous for the acccurate determination of Mg 2+ .