117828246

Low Temperalure TLC-MS of Essentiai Oils

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Figurę 5

Denstt ogram (a), vłdeo*can (b) obtaJned from the essentiai oll o! 5. nemorosa, and mass spectra of separated chromatographłc banda

(1H5)-

tions, which arc markcd with numeraJs on the densitograms and the videoscans. From visual inspection of the densitograms and the mass spectra it is clearly apparent that the species bclonging to the Sahia gcnus differ substantially in respect of their finger-prints and hence, their Chemical composition also.

An interesting fcature characterizes individual sets of mass spectra recorded for the different sagę species. It is readily apparent that the mass spectra of the fractions with the highest R_y value (i.e., the fraction 5 in Figures 2-5) fumish much sim-pler fingerprints than those closer to the origin. In Figurę l (S. lavanJulifolia\ this regularity was not observed though, because mass spectrum no. 4 was recorded for the sum of the two rather poorly separated fractions. Reproducibility of this characteristic pattern has been confirmed by muhiple repetition of the TLC-MS analysis. This shows that each essentiai oil con-tains greater amounts of high-polarity compounds (e.g._t ter-penoids), which are morę strongly retained in adsorption chro-matography, thus yiclding lowcr R_f values, than of low-polarity compounds (e.g., terpenes). It is also possible that the low-polarity components of the oils (rcpresented by peak 5 in Figures 2-5) are less strongly adsorbcd by the silica gel layer and, hence, at ambient temperaturę partially evaporate or sublimc

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Journal of Planar Chromatography 23 (2010) 4