Competitive solvent extraction of alkali metal cations into chloroform by lipophilic acyclic proton-ionizable polyethers

Article abstract of DOI:10.1021/ac00039a011

A series of lipophilic acyclic polyether carboxylic acids and a corresponding polyether phosphonic acid monoethyl ester were synthesized in which the unit that contains the lipophilic and the proton-ionizable groups is held constant, but the polyether chain and its terminal group are systematically varied. Competitive solvent extraction of alkali metal cations from aqueous solutions into chloroform was performed to assess the influence of structural variation within the extractant molecule upon the extraction selectivity and efficiency. Many of the ionophores exhibited extraction selectivity for Li⁺. One of the simplest chelating agents gave an extraction selectivity order of Li⁺ ? Na⁺ > K⁺,Rb⁺ > Cs⁺ and a Li⁺/Na⁺ selectivity ratio of 4.9, while the selectivity ratios for Li⁺ over K⁺, Rb⁺, and Cs⁺ were 12 or higher.