IMMOBILIZATION OF SILVER AND PLATINUM IONS FOR METAL AFFINITY-CHROMATOGRAPHY

Ag(I) or Pt(II) are immobilized onto a polyacrylamide resin using a gl utaraldehyde/thiourea activation procedure. Wet chemical experiments a nd X-ray photoelectron spectroscopy indicate that metal ion immobiliza tion is due to chemical complexation with thiourea. Immobilization usi ng thiourea results in significantly lower metal loss from the solid p hase as compared to ion exchange immobilization and allows for the use of chloride and phosphate salts in the mobile phase. The immobilized Ag(I) resin retains amino acids in the order: histidine > methionine > > tryptophan >> tyrosine > phenylalanine > asparagine > proline; using a phosphate buffer mobile phase at pH 7. At pH 4.7, methionine is ret ained longer on the Ag(I) resin than histidine. The affinity of methio nine for the immobilized Pt(II) resin is greater giving the order: met hionine (not eluted) >> tryptophan > tyrosine > histidine = phenylalan ine; using a phosphate mobile phase at pH 7.