Gy Kátay

Comparison of thin-layer chromatography and overpressured layer chromatographic techniques for the separation of ascorbigen and 1'-methylascorbigen

Abstract Simple and efficient methods are described for the separation of biologically active ascorbigen and 1′-methylascorbigen by normal-phase TLC, conventional as well as new personal overpressured layer chromatographic (OPLC) systems using the same eluent. Results obtained with these techniques were compared on the basis of the separation parameters with special emphasis on the presentation of the advantages of the automated personal OPLC system. For the characterization of the personal OPLC system dependence of average plate height and resolution on the external pressure, front velocity and development distance was examined on TLC and HPTLC sorbent layers using ascorbigen and 1′-methylascorbigen as model compounds.

Critical evaluation of experimental conditions influencing the surface-enhanced Raman spectroscopic (SERS) detection of substances separated by layer liquid chromatographic techniques

SummarySurface-enhanced Raman spectra (SERS) ofp-dimethylaminobenzylidenerhodanine have been recorded on silica gel 60 F254 and Si60 F254 Raman TLC plates. Spectra were enhanced by use of a silver sol prepared according to the modified Lee-Meisel procedure. The standard deviations of the intensities and the band ratios for the seven most intense peaks were calculated for 30 parallel measurements. Although the Raman plate gives more reproducible results, several experimental difficulties are encountered in the development of chromatograms.SERS detection of ascorbigen and 1′-methylascorbigen was performed after chromatography on silica gel 60 F254 TLC and HPTLC plates and on Si60 F254 Raman TLC plates. Traditional development was used for the silica gel 60 F254 TLC plates and Si60 F254 Raman plates, and the personal OPLC technique for the silica gel 60 F254 HPTLC plates. It was found that the SERS spectrum gave information about the indole ring only. Because bonding of the analyte to the stationary phase results in a change in molecular conformation-in contrast with the behaviour of rhodanine-the type of the plateused and the development procedure employed can significantly influence the quality of the SERS spectrum.