液膜型NN金属指示薬イオン選択性電極の作製とキレート滴定への応用

概要

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A liquid membrane type NN metallochromic indicator ion-selective electrode is constructed and its application to chelatometric titration of calcium(II) is described. The familiar NN indicator {2-hydroxy-1-(2-hydroxy-4-sulpho-1-naphthylazo)-3-naphthoic acid, Patton and Reeder's dye} is widely used as a metallochromic indicator for the chelatometric titration of calcium(II). With zephiramine (benzyldimethyltetradecylammonium chloride, abbreviated as Zeph+Cl^-) or benzylcetyldimethylammonium chloride (abbreviated as BCMA+Cl^-), the NN indicator ion forms an ion-pair in aqueous phase, which is easily extracted into nitrobenzene (NB) phase. The extracts show the property of H_3NN^- ion-sensitive membrane. The calibration curve of the electrode composed of Zeph+_H_3NN^- membrane shows the Nernstian response for H_3NN^- ion in the range of negative logarithm of the concentration from 3 to 6.5 and the slope of which is 58 mV per activity decade. Effect of pH on the electrode potential was observed and the potential of the electrode composed of Zeph^+-H_3NN^-membrane is constant over the pH range from 4.5 to 13.0. Selectivity coefficients of the electrode were evaluated by means of the mixed solution method. The present electrode shows good selectivity over most common inorganic anions. Calcium(II) was successfully titrated with the aid of the present electrode and the result showed a good agreement with that obtained by visual method.
1980-07-05