PREPARATION OF SODIUM ION-SENSING PLATES BASED ON A THIN-LAYER LIQUIDMEMBRANE CONTAINING A NEUTRAL IONOPHORE AND A LIPOPHILIC ANIONIC DYE

A sodium ion-sensing plate was prepared as an easily-handled ion sensi ng optical chemical sensor (optode) probe. The sensing plate consisted of an ion-sensing liquid thin layer containing a Na+-selective neutra l ionophore (16-crown-5 derivatives) and a lipophilic anionic dye (KD- A3), which was placed on a chemically modified (octadecyl silanized) f rosted glass plate that was covered with a cellulose dialysis membrane . This ion-sensing plate can easily determine Na+ ranging from 10(-4) to 10(-1) M by simply dipping the I!late into the sample solution. The response time was ca. 80 s for 10(-1) M NaCl with good reproducibilit y (relative standard deviation (RSD)=+/-1.33 % for ten sequential meas urements).