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 cdmpounds exhibited clear Mg2. - selectivity under high pH conditions(pH10). Especially, the electrode based on 2-acetyl-l-tetralone shows excellent Mg2. -se1ectivity, and the selectivity coefficients of the Mg2+ -electrode to Ca2+, K+ and Na+(log [formula omitted] log [formula omitted] and log [formula omitted]) in pH 10 solution were -2.2, -1.9 and -2.7, respectively. This electrode gave a response slope of about 60 mV/pMg2+ ranging from 1 Χ 10-4 to 2 Χ 10-2 M Mg2+, which corresponds to twice the usual Nernstian theoretical response slope for the divalent cation. This phenomenon is advantageous for the accurate determination of Mg2+.
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