COUPLING OF COLUMN LIQUID-CHROMATOGRAPHY AND SURFACE-ENHANCED RESONANCE RAMAN-SPECTROSCOPY VIA A THIN-LAYER CHROMATOGRAPHIC PLATE

Surface-enhanced resonance Raman (SERR) spectroscopy was used to chara cterize compounds separated by column liquid chromatography (LC). Thre e percent of the effluent from a conventional-size LC column were immo bilized on a moving thin-layer chromatography (TLC) plate using a spra y-jet solvent-elimination interface. Next, colloidal silver was applie d to the analyte spots and in situ SERR spectra were recorded with a m ultichannel micro-Raman spectrometer. Storage of the LC effluent avoid s the need to use a continuous flow of colloidal silver and, in princi ple allows compounds to be detected independently of LC conditions lik e eluent composition and flow rate. Using dyes as test compounds, the method was optimized and aspects were studied such as type of TLC plat e, LC separation of the dyes, preservation of LC integrity during immo bilization, and SERR analysis of the deposited compounds. With a silic a TLC plate as deposition substrate, good-quality and characteristic S ERR spectra were obtained for the dyes which were separated on a cyano proyl-modified silica LC column with methanol-water containing the vol atile additives ammonium acetate and triethylamine as eluent. The mini mum identifiable concentration of the dyes was about 250 ng ml(-1) (75 0 pg applied on the plate). For some strong Raman scatterers such as n ile blue and pararosaniline, the major spectral peaks could be observe d down to concentrations of 25 ng ml(-1).