TLC-MS VERSUS TLC-LC-MS FINGERPRINTS OF HERBAL EXTRACTS. PART I. ESSENTIAL OILS

Abstract

In our earlier studies, we proposed the low-temperature thin-layer chromatography with densitometric and mass spectrometric detection for fingerprinting of essential oils derived from several different species from the Salvia genus. Development of the proposed LT-TLC-MS approach was only possible with use of the TLC-MS interface able to couple the chromatographic plate with mass spectrometer. The goal of this study was to develop for the same purpose the two-dimensional liquid chromatographic system, which was only possible with use of the TLC-MS interface. It included the low-temperature thin-layer chromatography coupled with high-performance liquid chromatography, to build an overall LT TLC-LC-MS system. We compared the fingerprinting results for the essential oil of Salvia lavandulifolia obtained with use of the one-dimensional system (1D LT TLC-MS) with those obtained with use of the two-dimensional system (2D LT TLC-LC-MS). It was shown that the 2D approach provides more fingerprints for further investigations than the 1D approach. Moreover, it is also clear that the 2D approach is better suited for identification of individual chemical species contained in a given mixture, due to the simpler patterns of mass spectra obtained from the 2D analytical mode than from the 1D one. However, with the constituents of the essential oil derived from Salvia lavandulifolia, a straightforward identification was not possible, basically due to numerous groups of isomers among the terpenes and terpenoids contained in the examined sample that have the same molecular weights and hence, can give identical m/z signals.

Keywords:

• essential oils
• low-temperature TLC-LC-MS
• low-temperature TLC-MS
• mass spectrometric fingerprinting
• Salvia spp.

ACKNOWLEDGMENT

The work of two authors (Ł.W. and D.S.) was partially supported by the PhD scholarship granted to them in 2009 within the framework of the “University as a Partner of the Economy Based on Science” (UPGOW) project, subsidized by the European Social Fund (EFS) of the European Union. The work of one author (M.N.) was supported by the post-doctoral grant no. 142062, subsidized by the Ministry of Science of Serbia. The authors wish to express their gratitude to Mrs. Małgorzata Zych from Donau Lab (Polish representative of the firm CAMAG) for kindly lending them the CAMAG TLC–MS interface and, in that way, enabling this research.