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preliminarily separated by means of LT TLC (see Fig. l(o)). Each of these three figures shows the liquid chromatogram registered in the positive ionization modę, with the separated chromatographic bands indicated on it with numerals (l)-(4) (Figs 2 and 3), or (l)-(3) (Fig. 4). For each of these separated bands the respective mass spectra were registered, which are shown in Figs 2(a)-(d), 3(a)-(d), and 4(a)-(c).

The employed LT TLC-LC-MS system couples together the normal phase thin layer chromatographic modę (executed on the silica gel layer) with the classical reversed phase liąuid chromatographic modę (performed with use of the C18 column). The sum of the separated chromatographic bands shown in Figs 2(o)-4(o) is higher than that shown in the densitogram (see Fig. l(o)). In Figs 2(o)-4(o), we can see liąuid chromatograms of fractions 1-3, seąuentially eluted by means of the TLC-MS interface from the chromatographic piąte to the 2D analytical system (see Fig. l(o)). According to the reversed-phase retention mechanism, the second-step fractionation on the liąuid chromatographic column results in the diminishing polarity seąuence of the secondarily subdivided fractions (i.e., of fractions 1-4 in Figs 2 and 3, and fractions 1-3 in Fig. 4). Thus, the application of the 2D LT TLC-LC-MS system provides morę accurate information about composition of a complex mixture than the ID LT TLC-MS system. However, the results obtained for the investigated Salvia lavandulifolia sample can again be considered as the morę refmed fingerprints only, especially if considered in an absence of the standard compounds (which often is a sufficient enough goal in phytochemical research though).

If we take a morę accurate view of the mass spectra shown in Figs 2(a)-(d), 3(a)-(d), and 4(a)-(c)), then we will notice the presence of certain signals which are characteristic of practically all spectra originating from the 2D LT TLC-LC-MS modę and which are absent from the ID LT TLC-MS modę spectra (Figs l(a)-(c)). Most probably, these signals can be related to the isoprene unit and their respective m/z values eąual to 71, 87, 89, and 126. These signals can probably be attributed to the [CsHg + H + He] *, [CsHg + H₂0 + H]⁺, [CsHg + H₂0 + H + He]⁺, [CsHg + H + He + MeOH]' ions, respectively. From this observation, a conclusion can be drawn that the 2D techniąue applied to essential oils seems morę destructive than the ID techniąue.

As it comes out from the literaturę [24], essential oils originating from the Salvia genus are relatively rich in diterpenoids of the abietane type, with the respective molecular weights contained within the rangę from 240 to 344 Da (the latter molecular weight valid for galdosol), and in triterpenoids, with the respective molecular weights contained within the rangę from 427 to 473 Da. Thus it can be anticipated that the numerous signals present in the