Abstract
Two new chromogenic crown reagents, 22-Kosh and 21-Kosh, have been synthesized by the condensation of Cryptand-22 and -21, respectively, with 2-hydroxy-5-nitrobenzyl bromide. Extraction of alkaline-earth metal ions with a dichloroethane solution of 22-Kosh or 21-Kosh has been investigated and their extraction coefficients have been evaluated. The relative ease of extraction is Mg《Ba<Sr<Ca for both reagents. The extraction is more effective with 22-Kosh than with 21-Kosh, and the selectivities for alkaline-earth metal ions are more pronounced with 21-Kosh than 22-Kosh. 22-Kosh is found to be a very promising reagent for the extraction-photometric determination of calcium in blood serum. The molar absorptivity of the calcium complex is 5.5×104 l·mole−1·cm−1 at 406 nm.
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