Fiber-optic Raman spectroscopy was adapted to measurements of metal-ion complexation by silica-immobilized 8-hydroxyquinoline (8HQ) under conditions typical of metal-ion preconcentration or recovery applications.
The extraction of metal ions from aqueous sources onto immobilized ligands is useful in environmental clean-up initiatives and in the preconcentration of metal ions for ultratrace detection. In situ
vibrational spectroscopy of metal complexation by silica-immobilized ligands can assist in the development of these applications. In the present work, in situ Raman spectroscopy and flow methods
allowed the reactivity of silica-immobilized 8HQ with Cu2+ to be investigated. The structure of the complexed and uncomplexed neutral and protonated forms of the ligand could be resolved and
quantified in Raman spectra taken under different solution conditions. Spectra of the ligand bound to different metal ions could be distinguished as well. Raman spectra taken under batch sampling conditions
were able to confirm a 1:1 metal/ligand stoichiometry of the silica-immobilized 8HQ complex, which was reasonable in light of the surface coverage by the ligand. In situ monitoring under flowing
solution conditions allowed changes in the state of binding to be followed in real time.
Department of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, Utah 84112-0850
Publication date: December 1, 2000
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