Pyrazole-Containing Crown Ethers as Ionophores for NH₄⁺-Selective Electrodes

Abstract

The pyrazole-containing 18-membered crown ether 1, which possesses a less-bulky substituent on the sp³ nitrogens and not only the sp² nitrogen, but also the carbonyl groups as ligating points, exhibited excellent ability as an ionophore for a NH₄⁺-selective electrode. The value of the selectivity coefficient of an ion-selective electrode (ISE) containing 1 for the NH₄⁺ ion with respect to an interfering K⁺ ion was 6.3×10^-2. This result is superior to that of ISE based on an antibiotic substance, nonactin (1.2×10^-1).