Gold-containing chromatographic beads were used to record spectra of the tripeptide glutathione and the protein immunoglobulin G (IgG) by surface-enhanced Raman scattering (SERS) spectroscopy. SERS spectra were recorded from glutathione in solution at three different pH values, 2, 6 and 10. It was found that the SERS spectra are strongly dependent on pH, which indicates that the adsorption mode of glutathione changes with the pH value of the solution. Assignment of some of the observed bands and a suggestion for adsorption modes at the different pH were made. A SERS spectrum of human IgG in ethanolamine was also recorded. No complete assignment of the bands in this spectrum was performed, but the results indicate adsorption to the gold nanoparticles by aromatic amino acids and cystine residues.

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Porous polymer beads with a large inner area were used as a stabilizing matrix for SERS-active gold particles. A commercially available ion exchanger .SOURCE TM / was used together with HAuCl 4 . Absorbance measurements and an x-ray diffraction study confirmed that nanocrystalline gold was obtained in the polymer beads. Transmission electron microscope measurements were performed and showed that larger nanoparticles, 20-100 nm, were obtained on the surface, whereas in the interior smaller particles, approximately 2-10 nm, could be found. Three analytes, mercaptoethanesulfonate, mercaptopropionic acid and thiocyanate, were adsorbed on the gold particles inside the polymer beads. From all analytes enhanced Raman spectra could be obtained. The distribution of analytes adsorbed on gold nanoparticles was investigated by confocal Raman spectroscopy. SERS spectra from the analytes could be observed throughout the polymer bead, indicating a fairly uniform distribution of analytes adsorbed on gold nanoparticles.

Confocal Raman spectroscopy and confocal scanning laser microscopy have been used to analyze ligand distributions within individual chromatographic adsorbent particles. Three different types of particles have been investigated. The first type was synthesized to have a uniform distribution of allyl groups, whereas the two others were designed to have a surface layer of sulphopropyl groups and cores containing allyl groups and dextran, respectively. With confocal Raman spectroscopy it was possible to follow the distribution of both the surface layer and the interior. The distribution of sulphopropyl groups was evaluated with both confocal scanning laser microscopy and confocal Raman spectroscopy, whereas the distributions of allyl groups and dextran were evaluated only with the latter method. The results from the confocal measurements showed the expected result with a uniform distribution of allyl groups in the first type of particle and surface layers of sulphopropyl groups and cores with dextran or allyl groups for the two others.

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