## 3 Results
### Edible Oils Classification Based on Raman Spectroscopy  
The chemometric treatment was separately performed on two spectral ranges: 600-1200 cm\({}^{-1}\) and 1200-1780 cm\({}^{-1}\), because of the high size of experimental data set. The statistical data processing of the first spectral area 600-1200 cm\({}^{-1}\) indicated a lower discrimination potential as compared with that from 1200 to 1780 cm\({}^{-1}\) for the investigated oil sample classification. Therefore, the subsequent data analysis was performed on the 600-1200 cm\({}^{-1}\) spectral area. The simultaneous classification of all six oil species (1--sunflower, 2--sesame, 3--hemp, 4--walnut, 5--linseed, and 6--sea buckthorn), performed by applying stepwise LDA, allowed a separation of 100 and 91.3% in initial and cross-validation classification, respectively. The lower percentage which was obtained in cross-validation procedure as compared with the maximum achieved for initial classification is due to the wrong attribution of some samples to other categories as follows: samples LIN 17 (linseed) and SB 21 (sea buckthorn) that were assigned to the walnut oils group. Figure 3 presents the representative Raman spectra for the six types of the investigated oils and the markers which allowed their classification; these signals are: 1443, 1523, 1649, 1666, and 1780 cm\({}^{-1}\)  
The bands observed for the simultaneous classification can be tentatively assigned as follows: 1443 cm\({}^{-1}\) to the CH deformation (CH\({}_{2}\) group) from the saturated part of oils [15], 1523 cm\({}^{-1}\) to the C=C stretching vibration from carotenoids [16], 1649 and 1666 cm\({}^{-1}\) to the C=C stretching vibration from _cis_ conjugated systems and _trans_-CH=CH- groups [17; 18], while 1780 cm\({}^{-1}\) could be assigned to the C=O stretching vibration from some minor constituents--e.g., aspartic/glutamic acid residue [19] that exist in significant amounts in the appropriate seeds (e.g., hempseeds) [20]. Considering these data, we observed that the oils discrimination is mainly based on the peaks associated to the saturated part, to _cis_ or _trans_ configurations, to a characteristic band from carotenoids, or to a specific band (C=O) from different minor ingredients found in some oils. In order to emphasize the characteristic features of each oil type, a separate differentiation between every specific oil variety as compared to the remaining samples was made. In this regard, the first performed differentiation was made between the sunflower oil and the rest. The separation that was achieved was 100% in both initial and cross-validation procedures based on the following discriminator signals: 1267, 1434, and 1458 cm\({}^{-1}\). According to literature, these bands are assigned to the CH deformation vibration from _cis_-CH=CH- [18; 21], to CH\({}_{2}\) deformation vibrations adjacent to double bond, and asymmetric CH\({}_{3}\) deformation vibration, respectively [17]. It is clear that for the sunflower oils, the differentiation is based on the deformation vibrations from _cis_ and saturated fragments of the oils. The same percentage was achieved for the separation of hemp oil from the rest of the samples; this time the discrimination signals are 1775 and 1780 cm\({}^{-1}\), which could be attributed to the C=O  
Figure 3: Raman spectra for the six types of oils with the main marker bands employed for the simultaneous classifications. vibrations from the amino acid residue found in the hempseeds and, also as minor constituents, in oil [19; 20]. A good separation was obtained for the sea buckthorn oil type (95.7%) in both initial and cross-validation procedures, based on the signals from 1463 and 1525 cm\({}^{-1}\), specific to the CH\({}_{2}\)/CH\({}_{3}\) group deformations [22] and C=C stretching vibrations from carotenoids [16]. This separation percentage resulted because one sea buckthorn sample was wrongly attributed, being overlapped with the group formed by the rest of the samples.