## 1 Introduction  
Volatile sulfur compounds (VSCs) are known to have a great impact on the aroma of various food and beverages, especially because of their abundance and low detection threshold. Their presence plays an important role in the aroma of foods such as vegetables, cheese, coffee, chocolate, UHT milk, as well as wine and beer [1]. In fermented beverages, sulfur compounds are formed as a result of both enzymatic (yeast fermentation) and nonenzymatic (chemical and thermal reactions during production process) pathways, and most of them are generally responsible for off-flavors in final products (rotten eggs, burnt rubber, cooked cabbage, etc.) [2, 3]. Especially, VSCs are in the main area of interest of wine and beer producers as they often cause aroma defects in the final products [3, 4, 5]. The presence of VSCs in distilled beverages has not been studied in such a great manner as it has been for wine and beer. Distilled (or spirit-based) beverages are produced worldwide from a wide variety of raw materials and include among others whiskey, rum, tequila, vodka, and brandy. Among them, brandies (both grape brandies and fruit brandies) are receiving increasing interest because of their unique flavor characteristic. Fruit brandies are produced by fermentation of fresh fruits or fruit mash and subsequent distillation of fermented mash at less than 86% \(\omega\)/\(\upsilon\) alcohol content to maintain the aroma and flavor of used raw material. Often, after distillation, the maturation (aging) of distillates in wooden casks is carried out. The maturation lasts from several months to several years, and the final product gains characteristic flavor dependent on the maturation conditions [6; 7; 8]. Depending on the used raw material, brandy's name is preceded by the name of the fruit used in the production, e.g., apple brandy (e.g., Calvados), plum brandy (e.g., Slivovitz, Zwetschgenwasser), cherry brandy (e.g., Kirsch), or pear brandy [6; 9]. The determination of VSCs in fermented beverages is difficult due to their low concentration in analyzed samples, and, for that reason, selecting the appropriate method of sample preconcentration is often necessary. The techniques that could be used to extract the volatile compounds from samples are liquid-liquid extraction (LLE) [10], static [11] or dynamic [12] headspace, stir bar sorptive extraction (SBSE) [13], vacuum distillation [14], solvent-assisted flavor evaporation (SAFE) [15], counter-current supercritical fluid extraction [16], and solid-phase microextraction (SPME) [4; 17]. Among them, the SPME method has gained greater attention and has been successfully used in the determination of volatiles from solid [17], liquid [18], and gaseous samples [19]. SPME can be performed by either direct sampling (DI-SPME) or by analyzing the headspace above the sample (HS-SPME) [20]. SPME is an inexpensive, simple, and solvent-free technique of extraction of volatiles from the sample, and what is more, this method has good reproducibility and easily can be automated [20]. However, the appropriate experimental conditions must be first settled to ensure the effective extraction of the compounds of interest. The parameters that are crucial for SPME analysis are the selection of fiber (its polarity and thickness), extraction time and temperature, addition of soluble salts (sodium chloride, sodium hydrogcarbonate, potassium carbonate), agitation of the sample, and the concentration of analyte in the sample [20]. In case of analysis of samples containing alcohol (beer, wine, spirits) the concentration of ethanol has a great impact on the sensitivity of analysis when sulfur compounds are taken into consideration [21; 22; 23]. In this work, the influence of such parameters as the concentration of ethanol, addition of sodium chloride and EDTA to the sample prior to extraction, time and temperature of the process, as well as 5 different fiber coatings were analyzed with regard to 22 volatile sulfur compounds that can be found in fermented beverages.