Immobilization of silver and platinum ions for metal affinity chromatography

Ag(I) or Pt(II) are immobilized onto a polyacrylamide resin using a glutaraldehyde/thiourea activation procedure. Wet chemical experiments and X-ray photoelectron spectroscopy indicate that metal ion immobilization is due to chemical complexation with thiourea. Immobilization using thiourea results in significantly lower metal loss from the solid phase 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 retained longer on the Ag(I) resin than histidine. The affinity of methionine for the immobilized Pt(II) resin is greater giving the order: methionine (not eluted) > tryptophan > tyrosine > histidine = phenylalanine; using a phosphate mobile phase at pH 7.