Effect of Na on solvent extraction of alkaline earth metal cations by proton-ionizable calix[4]arenes
نویسندگان
چکیده
Metal ion recognition by proton-ionizable calixarenes is often affected by interference from the Na present in many aqueous solutions. To assess the Na-effect on calixarene selectivity towards alkaline earth metal cations (AEMC), competitive solvent extraction of Mg, Ca, Sr, and Ba from aqueous solutions into chloroform by di-ionizable calix[4]arene N(trifluoromethylsulfonyl)carboxamides and corresponding carboxylic acids, conformationally mobile and restricted to cone, partial cone and 1,3-alternate conformations, was investigated in the absence and in the presence of aqueous-phase Na. The extraction selectivities were found to be altered due to contrasting Na-induced changes in the AEMC uptake. Observed increases in loadings of smaller AEMC are rationalized by their co-extraction with Na.
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