## 3 Results and Discussion
### Application to Real Samples  
The optimized and validated SBSE-GC-MS method was applied for the analysis of thirty-four different samples obtained under different conditions (Appendix A, Table A1). Each sample was analyzed in duplicate. The results are shown in Appendix A (Table A2). Low standard deviations for each sample were obtained, indicating good precision values. DES was not detected in any sample, whereas DEDS was only detected in four samples. The most significant volatile sulphur compounds found in the samples were DBS, DMDS, and  
Figure 2: Green character assessment of the present work and different analytical methodologies from bibliography (Table 5): [PERSON] et al., (2009) [1]; [PERSON] et al., (2016) [4]; [PERSON] et al. (2020) [11]; [PERSON] et al. (2007) [12]; [PERSON] et al. (2017) [13]; [PERSON] et al. (2020) [14]; [PERSON] et al. (2019) [19]. Colour codes: red: very low green character; orange: low green character; yellow: medium green character; green: high green character. DPS. DMTS and TC were detected in a low number of samples from both column and pot still distillation. The mean concentrations for DBS and DMDS were 642.1 \(\pm\) 696.8 \(\upmu\)g/L and 185.8 \(\pm\) 452.1 \(\upmu\)g/L, respectively. The high standard deviations associated with the mean values obtained for all of the volatile sulphur compounds implies that their concentrations depend on several different factors such as raw wine, specific conditions for distillation, and possible aging in wood, among others. [PERSON], [PERSON], [PERSON], [PERSON], and [PERSON] [30] found dimethyl disulphide (DMDS, from 50 to 500 \(\upmu\)g/L of pure alcohol (PA)), dipropyl sulphide (DPS), dibutyl sulphide (DBS, from 20 to 100 \(\upmu\)g/L of PA), dipropyl disulphide (DPDS), and 2-thiophenecarboxdehyde (up to 1000 \(\upmu\)g/L in some samples), among other volatile sulphur compounds, in Cognac samples, whereas dimethyl sulphide (DMS) was detected in brandy samples [10]. 2-thiophenecarboxaldehyde was also found by [PERSON] et al. [5] in the heart and tail fractions of a spirit obtained from Spine grape wine. In order to evaluate the similarity among all of the samples, taking into account the content of volatile sulphur compounds considered in the present work, the data were subjected to a Cluster Analysis (CA) considering the squared Euclidean distance as a metric and the Ward method as an amalgamation rule. As can be seen in Figure 3, the samples seem to be grouped according to the use of sulphur dioxide, with three groups: one of them with distillates without SO\({}_{2}\) and aged in wood, and two others with SO\({}_{2}\). [PERSON] et al. [31] found that the addition of sulphur dioxide during alcoholic fermentation had the higher influence on the aromatic and phenolic profile of distillates obtained using different distillation methods and aged for 14 and 28 months in oak wood. In the present study, samples 25, 27, 29, and 31 correspond to samples 24, 26, 28, and 30, respectively, after different periods of aging in wood. Out of all of them, 26, 28, and 30 were obtained from wines subjected to the addition of SO\({}_{2}\). As can be observed in Table 2, in general, all of the volatile sulphur compounds were found to be decreased in the aged samples compared to unaged ones. In this sense, [PERSON] et al. [32] found that the content of sulphur volatile compounds together with alcohols, aldehydes, and terpen decreased with aging time in different brandy samples. In this sense, [PERSON] et al. [33] found that dimethyl sulphide increased in Shiraz wines during accelerated bottle aging and that those increases were higher when more impermeable closures were employed, suggesting that its formation depends on the redox status of the wine. The same behaviour was observed for dimethyl disulphide by [PERSON] et al.