###### Abstract  
Varietal volatile compounds are characteristic of each variety of grapes and come from the skins of the grapes. This work focuses on the development of a methodology for the analysis of free compounds in grapes from Trincadeira, Cabernet Sauvignon, Syrah, Castelao and Tinta Barroca from the 2021 and 2022 harvests, using HS-SPME-GC \(\times\) GC-TOFMS. To achieve this purpose, a previous optimization step of sample preparation was implemented, with the optimized conditions being 4 g of grapes, 2 g of NaCl, and 2 mL of H\({}_{2}\)O. The extraction conditions were also optimized, and it was observed that performing the extraction for 40 min at 60 \({}^{\circ}\)C was the best for identifying more varietal compounds. The fiber used was a triple fiber of carboxen/divinylbenzene/polydimethylsiloxane (CAR/DVB/PDMS). In addition to the sample preparation, the analytical conditions were also optimized, enabling the adequate separation of analytes. Using the optimized methodology, it was possible to identify fifty-two free volatile compounds, including seventeen monoterpenes, twenty-eight sesquiterpenenes, and seven C\({}_{13}\)-norisoprenoids. It was observed that in 2021, more free varietal volatile compounds were identifiable compared to 2022. According to the results obtained through a linear discriminant analysis (LDA), the differences in volatile varietal signature are observed both among different grape varieties and across different years. HS-SPME-GC \(\times\) GC-TOFMS; flow modulator; varietal aroma composition; grapes; LDA 20242919899199199199199199199199199199199199191991991991991919919  
class, while the linalool family includes compounds like linalool, pyran oxides, and 2,6-dimethyl-2,7-ocatadien-1,6-diol, and finally, the geraniol class comprises citronellol and 3,7-dimethyl-1,7-ocatadiol. Sesquiterpenes are (C\({}_{15}\)) compounds consisting of three isoprene units in which an isopentenyl pyrophosphate (IPP) molecule reacts with a geranyl pyrophosphate (GPP) molecule to form farnesyl pyrophosphate (FPP) [9]. According to [PERSON] et al. 2014 [10] and [PERSON] et al. 2015 [11], sesquiterpenes have antioxidant, antibacterial, and anti-inflammatory properties. The content of these compounds affects the organoleptic characteristics of the grapes; hence, in the case of wines, for example, \(\alpha\)-bisabol and \(\alpha\)-calacorene are responsible for wood aromas and \(\alpha\)-copaene is responsible for a spice aroma [2; 12]. C\({}_{13}\)-Norisoprenoids are a group of aromatic compounds derived from enzymatic oxidative cleavage performed using carotenoid cleavage dioxygenases [13; 14]. \(\alpha\)-ionone and \(\beta\)-ionone are C\({}_{13}\)-norisoprenoids widely found in grapes, and result from the oxidative cleavage of carotenes, namely \(\alpha\)-carotene and \(\beta\)-carotene, respectively [15]. The oxidative cleavage of neoxanthine leads to the formation of a \"grasshopper\" ketone, which then undergoes enzymatic transformation and is finally catalyzed with acid to form \(\beta\)-damascenone [16; 17]. \(\beta\)-damascenone is known for its fruity-flaval notes or baked apple aroma [18]. These compounds are present in grapes in trace amounts (\(\mu\)g kg\({}^{-1}\)) and for their analysis a previous sample preparation step that enables the isolation and/or preconcentration of the analytes is mandatory [19]. Solid phase extraction (SPE) is the most used sample preparation technique for grape analysis. SPE was developed at the end of the 1970s to replace liquid-liquid extraction (LLE), since it requires high amounts of solvents and is time-consuming. SPE enables the concentration and purification of analytes through the use of a cartridge containing a selective sorbent [20]. Compared to the LLE technique, SPE is faster, has greater reproducibility, requires the use of a smaller amount of organic solvents, allows the extraction of several analytes simultaneously, and enables the isolation of compounds in different fractions [21].