METHOD OF DETECTING A SPECIFIC ION BY MEANS OF CROWN-ETHERS

To replace the conventional ion-sensitive field-effect transistor (ISF ET) ion sensor, an ion-sensing method using crown ether was developed. In this method, the alkaline metal ions (Na+ and K+ ions) were detect ed by the ac potential difference. Crown ether shows selectivity towar d alkaline metal ions, forming complexes. To investigate the selective characteristics of crown ethers using the ac potential difference, th ree types of crown ethers (18C6, 15C5, and 12C4) were used. The solven ts used were water, methyl alcohol, acetone, propylene-carbonate (PC), and dimethyl-formamide (DMF). Specifically, chlorides (NaCl, KCl, and CsCl) were dissolved in the solvent containing crown ether and the se dimentation potential was measured using a sedimentation-potential mea surement system. When 18C6 was used, the highest sedimentation potenti al of KCI was observed if PC was chosen for the solvent. When 15C5 was used, the highest sedimentation potential of NaCl was observed if met hyl alcohol was used for the solvent. It was confirmed that in order t o distinguish K+ and Na+ ions from other ions, PC containing 18C6 and methyl alcohol containing 15C5 should be used, respectively.