Applications of Macrocyclic Polyethers in Analytical Sensors and Ion Separation

Abstract

Artificial macrocyclic polyethers were synthesized and applied as neutral carriers for ion‐selective PVC membrane electrodes, ion‐chromatographic packing materials, extractants and adsorbents for ion separation, coating materials for piezoeletrical membrane sensors for organic species, and ion‐transport carriers through liquid membranes. Ion‐selective electrodes such as those for K+ Na+, UO22+, Cs+, Pb2+, Fe3+, Hg2+ and Ag+ ions based on crown ether‐phosphotungstic acid (PW) precipitates and dithio crown ethers respectively were prepared and showed good sensitivity and selectivity. Crown ether‐PW precipitates were applied as adsorbents of rare‐earth ions and some common heavy‐metal ions. Some rare‐earth ions were easily extracted with crown ethers, especially 15‐crown‐5. Poly(stytene/divinyl benzene) cryptand‐22 resin was synthesized and applied as a bifunctional stationary phase of ion chromatography to separate bom cations and anions, even some organic carboxylate geometric isomers. Crown ethers such as mono‐benzo‐15‐crown‐5 was successfully applied as a coating material on piezoelectric quartz membrane sensors for some organic species. The oscillation frequency of the crown‐ether quartz‐membrane sensor was sensitive to organic vapours such as amines and alcohols. Upon adsorption of organic species on the crown‐ether quartz membrane, the oscillation frequency of the sensor decreased obviously. Special crown ether such as dibenzo‐16‐crown‐5‐oxyacetic acid, decyl‐cryptand‐22 and 1, 4‐dihydro‐pyridine‐18‐crown‐5 were synthesized and successfully applied as ion‐transport carriers (ionophores) for transport of Na+ K+ and Mg2+ ions through liquid membranes.