SELECTIVE COLUMN CONCENTRATION OF ALKALI-METAL CATIONS WITH A CROWN-ETHER CARBOXYLIC-ACID RESIN

Column concentration of alkali-metal cations from dilute aqueous solutions with the polymethacrylic acid ion-exchange resin Amberlite CG-50 and with resins 1 and 2 obtained by condensation polymerization with sym-dibenzo-16-crown-5-oxyacetic and sym-(propyl)dibenzo-16-crown-5-oxyacetic acid, respectively, with formaldehyde is reported. Selective column concentration of alkali-metal cations was attained with resin 2, in which the pendent carboxylic acid group is oriented over the crown ether cavity. Due to the strong interaction of Na+ with resin 2, the elution peak for Na+ in the stripping solution was retarded relative to those of the other alkali-metal cations. With gradient stripping, the maximum concentration factor for Na+ from an aqueous sample solution which was 6.0 x 10(-5) M in each of the five alkali-metal cations reached 1030 with an 84% purity.