## 3 Results and Discussion
### Volatile Compounds  
The GC-MS analysis method is a combination of two analytical techniques: capillary column GC, which separates the components of a mixture and mass spectrometry (MS), which supplies the information necessary in the structural determination of each constituent. The results obtained following the SPME/GC-MS analysis is shown as chromatograms (Supplementary Figure S3). Their interpretation is achieved by identifying mass spectrum and the retention time. These two parameters significantly contribute to the identification of each volatile compound found in honey. Also, retention time has a determining role in many cases where the constituents show identical mass spectra. Following the SPME/GC-MS analysis, 79 constituents were identified the honey samples: 72 compounds samples from Transylvania (Zone 1), 57 compounds in samples from Southern Romania (Zone 2) and 66 compounds in samples from Eastern Romania (Zone 3). From all identified compounds, only 54 are common to all 50 samples. The chemotype changes from one region to another, and the difference is constituted by the 6 compounds found only in one region and 9 compounds in two of the regions. The interpretation of the chromatograms is achieved using the \"Data Analysis\" program. The noise level is set to 50 for the x-coordinate and the program goes over the chromatogram signal by signal according to this ratio. Identification of the compounds is achieved by comparing standard mass spectra from the \"Pal 600\" spectra library. The surface is calculated following the \"apexing mass\" model, which means measuring the surfaces in its entire mass. The next stage in the qualitative analysis is the calculation of the Kovats indexes. We have used this retention index in order to eliminate the relativity of the retention parameters by inserting some reference points in order to compare the retention times of chromatographic separation for each volatile compound found in honey. In this respect, a mixture of homologues n-alkanes (C\({}_{7}\)-C\({}_{30}\)) was used under the same chromatographic conditions (Sigma, Darmstadt, Germany), whose retention indices showed values between 600 and 2200. The retention indices specific to each compound is calculated as follows:  
\[\text{RI}=100\ ((\text{log tr}_{\text{i}}-\text{log tr}_{n})/(\text{log tr}_{n+1}- \text{log tr}_{n})), \tag{2}\]  
where: RI: compound retention index, tr\({}_{\text{i}}\): compound retention time, tr\({}_{n}\): retention time of the adjacent and anterior alkane, tr\({}_{n+1}\): retention time of the adjacent and subsequent alkane. The expression of the retention index uses two reference points: the alkane with the same number of carbon atoms in its molecule (\(n\)) as the volatile compound identified as i, which will elute before the compound, and the second reference will be the alkane with \(n\)+1 carbon atoms in its molecule, which will elute after the i compound. Table 7 comparatively shows the retention indices calculated RI\({}^{\text{b}}\) and the retention indexes found in literature. RI\({}^{\text{a}}\) corresponds to each volatile compound found and the type of column used (polar column). The main bibliographical source used was the PHEROBASE database, which is one of the most comprehensive and up-to-date. The main volatile compounds of acacia honey identified undoubtedly are: 3-methyl-3-buten-1-ol for Zone 1, ethanol, acetic acid, 5-ethenyldihydro-5-furanone for Zone 2, acetone, 3-methyl-3-buten-1-ol, _trans_-linal oxide, benzemethanol for Zone 3.