Resin polyamide crown ether

Also worth mentioning is the polyamide crown ether resin developed by Igawa et al. [39] for the separation of inorganic anions. The monomeric unit has the following structure ... 

Monomeric unit of a polyamide crown ether resin... 

The first stationary phases were prepared by packing columns with polymeric particles where benzo- or dibenzocrown ethers were cross-linked with formaldehyde in formic acid. The single crown ether molecules are bridged by methylene groups [71]. Dibenzo-18-crown-6 is a preferred starting material. Igawa et al. [76] also developed a polyamide crown ether resin to separate inorganic anions. 

Polymeric crown ether resins are mechanically unstable and are, therefore, operated with low flow rates between 0.05 and 0.1 mL/min resulting in long analysis times. Typical for all polymeric crown ether phases is the relatively low chromatographic efficiency, which does not meet today s requirements. However, this problem can be overcome by immobilizing crown ether polymers on the surface of a solid support. Modified and non-modified silica are predominantly used as support materials. Igawa et al., for instance, coated silica particles with the above-mentioned polyamide crown ether resin and obtained significantly better separations then with the rmcoated resin. 

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