Monitoring hydrogen sulfide de-novo formation from polysulfides present in wine using ion chromatography and ultra high-pressure liquid chromatography combined with fraction collection and high-resolution mass spectrometry

The study of polysulfides has been a recent topic of interest for wine research due to the possibility of these compounds to release hydrogen sulfide (H2S) during storage. However, studying these compounds has been challenging for several reasons. Polysulfides are low in concentration in natural samples, they are chemically unstable and pure standards of the single compounds (RSnR with n > 2) are not commercially available. In the present study, a method was developed in order to collect a single polysulfide and study its degradation and the consequent formation of H2S. For this approach, ultra-high pressure liquid chromatography was used with an integrated fraction collector and subsequently coupled to high resolution mass spectrometry. After fractionation, the degradation of the di-cysteinyl pentasulfide (CS5C) was induced by exposure to 30 °C and the H2S formation was measured in parallel using ion-exchange chromatography. This method showed the evolutions of different polysulfides and the H2S release originating from the target compound, an observation that to the best of our knowledge has never been made before. The method in the present study demonstrated promising applications for polysulfide studies and brought us a step closer to the understanding of the chemistry of polysulfides in wine