Study On The Identification Of Coptis Chinensis And Other Traditional Chinese Medicine Using TLC-SERS

Surface enhanced Raman spectroscopy(SERS) was one of the most prominent spectral analysis technologies in recent years, which was based on coupled optical responses of nanostructured metals and analyte molecules and the Raman signal of the molecules could be significantly enhanced when the molecules were adsorbed on roughened metal surfaces, such as colloidal nanoparticles. Compared to conventional Raman spectroscopy, SERS had many advantages, for it could provide strong spectral characteristics, effectively weaken the fluorescence, with short detection time and high detection sensitivity and so on. SERS could provide the information about the composition, properties and change rule of molecular structure of the adsorpted molecule, so as to be used for materials’ structure analysis and content determination. But SERS was not a separation technology, which made it not suitable to differentiate between the components in the mixture, as a traditional separation and analysis technique, thin layer chromatography method(TLC) was able to make up for this deficiency.Coptis chinensis, Flos Sophorae Immaturus and Stephania Tetrandra were taken as the research objects of this study, and a TLC-SERS method was developed to analyze the main active ingredient of the materials, which could realize the rapid identification of Traditional C hinese Medicine, as well as rich the Raman spectra database of their active ingredients. This article introduced the research from the following four aspects:(1) Silver colloid nano-particles were prepared using four different methods, and their enhancement effects were investigated using crystal violet as the molecular probe. Then a seris of modified measures were adopted to select the optimum sensitization substrate.(2) To establish a qualitative identification method for Traditional Chinese Medicine Coptis chinensis using thin layer chromatography coupled with surface-enhanced Raman spectroscopy(TLC-SERS). Firstly, Raman detection of berberine was carried out, which was the main active component of Coptis chinensis. Different types and different wavelength of excition light of Raman spectrometers were adopted to detect the powder of berberine, afterwards the conventional Raman spectra and the SERS spectra of different solvents(alcohol and water) and different concentrations of berberine solution were analyzed. Then the berberine component was separated from Coptis chinensis by TLC, and the SERS spectra of the spot for berberine on the thin layer was scanned in situ and compared with the normal spectra of reference substance for qualitative discrimination according to characteristic peaks. The method was simple, rapid, with good sensitivity and specificity. The spectra obtained needed no treatment, and the enhanced substrate was stable.(3) To establish a qualitative identification method for Traditional Chinese Medicine flos sophorae immaturus using TLC-SERS. The normal Raman spectra of main active ingredient reference substance, that was rutin, were obtained using different types of Raman spectrometers. Then the SERS spectrum of the spot for rutin ingredient on the thin layer was scanned and comparatively analyzed with the normal spectrum of rutin reference substance for qualitative identification according to characteristic peaks.(4) To establish a qualitative identification method for Traditional Chinese Medicine Stephania tetrandra using TLC-SERS. The normal Raman spectra of main active ingredient reference substance, that was Tetrandrine, were obtained using different types of Raman spectrometers. Then the SERS spectrum of the spot for Tetrandrine ingredient on the thin layer was scanned and comparatively analyzed with the normal spectrum of Tetrandrine reference substance for qualitative identification according to characteristic peaks.In summary, SERS method could obtain rich information of the molecular structure of the active ingredient in Traditional C hinese Medicine with high sensitivity and strong specificity. Using TLC method for separation of chemical composition of Traditional C hinese Medicine and combined with SERS method could obtain the molecular structure information of the main effective components in situ and sensitively, which provided a new idea and method for separation and fingerprint identification of main effective components of other Traditional C hinese Medicine.