Ion Chromatography on Poly(Crown Ether)-Modified Silica Possessing High Affinity For Sodium

Abstract

Stationary phases which have great affinity for Na⁺ were synthesized by incorporating 12-crown-4 polymer on silica gel for liquid chromatography of alkali and alkaline-earth metal ions. The stationary phases interact with Na+ most strongly of all alkali metal ions as expected, and the retention times on liquid chromatography of alkali metal ions were in the sequence Li⁺ < Cs⁺ < Rb⁺ < K⁺ < Na⁺. On the stationary phase, a mixture of Li⁺, Na⁺, and K⁺ can be separated completely by the elution with water/methanol mixture. By the use of spherical type silica gel instead of irregular type one and by effective end-capping of the residual silanol groups, the peak symmetry was improved significantly.