At-line coupling of surface-enhanced resonance Raman spectroscopy and reversed-phase ion-pair chromatography

At-line coupling of surface-enhanced resonance Raman spectroscopy (SERRS) and reversed-phase ion-pair chromatography with an excitation wavelength of 514.5 nm was applied for the isocratic separation and identification of four representative basic dyes (basic fuchsin, nile blue, crystal violet and ethyl violet). The effluent from a chromatographic column was deposited on a thin layer chromatography (TLC) plate by means of a spray-jet interface and analysed by Raman spectroscopy. The presence of non-volatile ion-pair reagents (1-heptanesulfonic acid sodium salt, sodium perchlorate) did not interfere with the deposition process and also not with the SERRS experiments. In fact higher SERRS intensities were observed in the presence of the ion-pair reagents. Reliable spectra could be recorded down to 90 pg of dyes deposited on the TLC plate.