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chromatography system eąuipped with mass spectrometric detection, off-line coupling the low-temperature thin-layer chromatographic system with high-performance liquid chromatograph (LT TLC-LC). In this two-dimensional system, the LT TLC part provides preliminary group separation of the essential oil components, with individual separated fractions one by one transported with aid of the TLC-MS interface not directly to mass spectrometer, but to the high-performance liquid chromatographic column first. Eventually, we used mass spectrometer as a detector, to obtain the LT TLC-LC-MS tandem system. However, any other HPLC detector can in fact be used for the analogous purpose as well (e g., the diodę array detector, DAD, the evaporative light scattering detector, ELSD, etc.)

The working conditions of TLC-densitometry and MS employed in this second analytical modę were exactly the same ones as in the earlier described case. Liquid chromatographic analysis with mass spectrometric detection (LC-MS) was carried out using an LC-MS System Varian (Varian, Pało Alto, CA, USA) equipped with a Varian ProStar model pump, Varian 100-MS mass spectrometer, and Varian MS Workstation v. 6.9.1 software for data acquisition and processing.

The LC analyses were carried out in the isocratic modę, using a Pursuit X Rs 3-C18 column (50 mm x 2.0 mm i.d.; Varian; cat. no. A6001050C020) and methanol as mobile phase at the flow ratę of 0.20 mL min'¹. Mass spectrometric detection and processing of the obtained results were carried out using the same working parameters as those described in the preceding sub-section.

RESULTS AND DISCUSSION

Composition of essential oils derived from Salvia lavanduli/olia has been investigated by numerous researchers and research groups [11, 13-24]. The literaturę survey on this subject resulted in a summary given in Table 1. As it comes out from the data collected therein, a vast number of the different terpenes and terpenoids with molecular weights roughly between 100 and 500 Da has been identified in essential oils originating from Salvia lavandulifolia and harvested from the different habitats and in the different vegetation seasons. The molecular weights of compounds found in these essential oils (listed in Table 1) helped to get a somewhat deeper insight in the mass spectra registered in our study for the different fractions of the essential oil derived from Sahia lamndulifolia and discussed in the further parts of this section.