Analysis of Varietal Thiols in Sauvignon Blanc Wines—Optimization of a Solid-Phase Extraction Gas Chromatography Tandem Mass Spectrometry Method

Odoriferous compounds 3-sulfanylhexanol (3-SH) and 3-sulfanylhexyl acetate (3-SHA), produced during the fermentation from precursors present in grape and must, are the most important representatives of the group of varietal thiols with a crucial role in the formation of the aroma of certain wines and a very low odor detection threshold. Due to their reactivity, polarity, high boiling points, and very low abundance in wine, isolation, and quantification of varietal thiols represent a tedious task. Procedures for the derivatization of varietal thiols in Sauvignon Blanc wine were conducted and optimized, with emphasis on the base selection, influence of pH value and duration on the outcome of derivatization, addition of antioxidants during the derivatization, and eluent selection. Varietal thiols and derivatives were isolated by solid-phase extraction and microextraction. Calibration was performed with standard addition combined with stable isotope dilution analysis. The developed methods were successfully used for the quantification of varietal thiols by gas chromatography–mass spectrometry with tandem mass spectrometry. Detection with a sulfur chemiluminescence detector, which was also performed, suffered from unsatisfactory sensitivity and higher standard deviations. For the first time, the concentration of varietal thiols in samples of Croatian Sauvignon Blanc wine was determined, with values ranging from 6 to 135 ng L−1.