N-(4-methylumbelliferone-8-methylene)-monoaza-15-crown-5 (1) and -18-crown-6 (2) extracted most efficiently lithium and potassium, respectively, from aqueous solution to 1,2-dichloroethane. The similar fluorescent crown ether derived from diaza-18-crown-6 (3) was selective to calcium. The fluorimetric determination of lithium and calcium was feasible by using 1 and 3, respectively.
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Nishida et al. (1982) studied this question.
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