Chromogenic benzo- and monoaza-12-crown-4, 13-crown-4 and 14-crown-4 lithium-selective crown ethers

Chromogenic benzo-12-crown-4, benzo-13-crown-4 and benzo-14-crown-4 ethers have been compared with monoaza-12-crown-4 and monoazal-13-crown-4 ethers. Of these compounds, monoaza-13-crown-4 exhibited the best analytical characteristics toward the selective determination of lithium. K(ex)Li/K(ex)Na was 525 for the monoaza-crown-4 compound.