Site distribution in resin beads as determined by confocal Raman spectroscopy

Scanning confocal Raman spectroscopy was used to study the distribution of reactive sites within a resin bead used for solid-phase synthesis. The distribution of NH2 groups in aminomethylated polystyrene resin (APS) was determined by doping with varying amounts of 4-cyanobenzoic acid. The extent of loading was determined by both elemental analysis and ninhydrin assays. The spatial distribution of the coupled 4-cyanobenzamide within the bead was determined to an in-plane resolution of 1 microm and depth resolution of about 4 microm, using the strong Raman CN stretching vibrational transition at 2230 cm(-1). Dry and swollen beads were studied and the distribution was found to be essentially uniform throughout the bead in all cases.