Surface-enhanced resonance Raman spectroscopy as an identification tool incolumn liquid chromatography

The compatibility of ion-pair reversed-phase column liquid chromatography a nd surface-enhanced resonance Raman Spectroscopy (SERRS) for separation and identification of anionic dyes has been investigated, with emphasis on the at-line coupling via a thin-layer chromatography (TLC) plate. SERR spectra using silver sols were recorded both for aqueous solutions and for samples deposited on aluminum:oxide and silica TLC plates at 514.5- and 457.9-nm l aser excitation. For some dyes, the shorter wavelength was needed to dimini sh the fluorescence background. For aqueous solutions and for samples depos ited on aluminum oxide, clear SERR spectra were obtained upon addition of p oly(L-lysine); for the silica plates, the addition of nitric acid was requi red. Upon drying the plates, the SERRS signals decreased in intensity; simp ly adding a drop of water could largely restore them. At-line coupling of L C and SERRS was successfully achieved when using silica, but not aluminum o xide, plates.,The application of a gradient, a high water content, and the presence of ion-pair reagents needed for the separation did not adversely a ffect the deposition and the recording of SERR spectra, The identification limits were 10-20 ng of deposited material, depending on the dye selected, which corresponded to injected concentrations of 5-10 mug mL(-1).