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 dist ribution of NH2 groups in aminomethylated polystyrene resin (APS) was deter mined 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 d etermined to an in-plane resolution of 1 mum and depth resolution of about 4 mum, 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.