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A new chromogenic crown ether 4″-cyano-2″, 6″-dinitro-4′-aminobenzo-15-crown-5 (HL) has been synthesized. Upon dissociation of the amine proton the yellow colored HL gives a purple anion L− and extracts K+ ion into chloroform as a colored complex. A linear range of 10–700 ppm K+ in the presence of excess Na+ is possible using this new chromogenic crown ether reagent.
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Pacey et al. (1980) studied this question.
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