Analytical Sciences

Secondary Equilibrium Chromatographic Evaluation of Polyether Complexation Using an Anion-Exchange Resin

Shamshad B. QURAISHI and Tetsuo OKADA ⁺

Department of Chemistry, Tokyo Institute of Technology, Meguro, Tokyo 152-8551, Japan

Secondary equilibrium chromatography has proved a useful tool for determining the polyether complexation constants. Both a cation-exchange and anion-exchange method can be used for this purpose. In the present paper, the applicability and versatility of the latter method, based on the surface complexation of polyethers with ammonium ions anchored on the stationary phase surface, are discussed, and compared with those of the former established method. The precision of the chromatographically determined complexation constants depends on the range of measured retention factors, suggesting that the surface charge density of the stationary phase can be optimized according to the retention ability of polyethers. The anion-exchange method is more versatile than the cation-exchange method from this viewpoint; i.e. the surface density of active groups (thus the retention range) can simply be controlled by preequilibrating the stationary phase with an aqueous solution of appropriate pH. (Keywords: Polyether complexation constants, secondary equilibrium chromatography, surface complexation with ammonium ions, methanol and acetonitrile)

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