Molecularly imprinted polymers on silica: selective supports for high-performance ligand-exchange chromatography.
Thin coatings of molecularly imprinted, metal-complexing polymers have been grafted to activated silica beads suitable for high-performance liquid chromatography (HPLC). Propylmethacrylate-activated silica particles were coated by copolymerization with a metal-chelating monomer, Cu(2+)-[N-(4-vinylbenzyl)-imino]diacetic acid, a metal-coordinating (imidazole) template, and ethylene glycol dimethacrylate. After extraction to remove the template and re-loading with metal, the composite materials re-bind the templates with which they were prepared and exhibit selectivities comparable to bulk-polymerized imprinted materials. The strong Cu(2+)-imidazole interaction, desirable for creating a high-fidelity imprint, leads to excessive retention in elution chromatography. By replacing the copper in the imprinted metal-complexing polymers with weaker-binding Zn2+, these novel ligand-exchange supports can effect partial to complete chromatographic separation of their bis-imidazole templates from other, highly similar imidazole-containing substrates. This "bait-and-switch" approach can significantly enhance the performance of molecularly imprinted materials. Scatchard plots of equilibrium binding data show a significant degree of heterogeneity in the imprinted binding sites of material prepared with a bis-imidazole template, but not with a mono-imidazole template. The best chromatographic separations are observed with small sample sizes, where the substrates occupy the strongest (highest-fidelity) sites.
Plunkett
S D
SD
Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena 91125, USA.
Arnold
F H
FH
D002614:Chelating Agents; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D003300:Copper / Q000737:chemistry; D008024:Ligands; D008855:Microscopy, Electron, Scanning; D011108:Polymers; D012822:Silicon Dioxide / Q000737:chemistry*; D015032:Zinc / Q000737:chemistry
D002614:Chelating Agents; D008024:Ligands; D011108:Polymers; D012822:Silicon Dioxide; D003300:Copper; D015032:Zinc