# Analysis of Potent Odour-Active Volatile Thioids in Foods and Beverages with a Focus on Wine
## 5 Conclusions and Outlook  
This review presents an up-to-date overview of the analysis of potent volatile thiols in foods and beverages, with a focus on wine analysis, because that is where many of the methodological advances have arisen. It covers topics from traditional selective extraction, chemical derivatisation (for LC or GC), chromatographic and MS instrumentation, matrix effects, and quantitation considerations. The identification of new volatile thiols and quantitation of known thiols have been made possible over the past three decades thanks to the development of specific thiol extraction methods in combination with sensitive analytical instrumentation. The major observations regarding the current state of potent volatile thiol analysis are: (1) extractions consisting of some form of thiol derivatisation are a popular choices due to their efficiency and simplicity; (2) GC coupled to different detectors (e.g., O, sulfur selective detectors, and MS) are still of considerable utility for discovering new thiol odorants, although newer LC-MS/MS approaches with thiol-specific derivatisation and precursor ion scan experiments also look promising; (3) recently developed quantitative LC-MS methods usually outperform existing GC-MS counterparts when considering the whole protocol, from isolation to analysis; and, (4) SIDA approaches are frequently applied for reliable quantitation. Undoubtedly, the analysis of potent volatile thiols has been greatly advanced; however, there is still room to further improve the analytical performances to develop faster, more cost-effective, and greener methods that can provide more comprehensive information. In terms of specific extraction, currently available techniques could be coupled with the popular MS detection for the sensitive analysis of volatile thiols. For instance, inspiration could be drawn from the analysis of low molecular weight thiols in water as their \(p\)-HMB-thiol complexes by LC-ESI-MS/MS after online SPE preconcentration [16]. This offers a stable, sensitive, and selective means for thiol analysis, although the use of mercury features again, and its application to potent volatile thiols in foods and beverages would still need to be investigated. New approaches that apply novel extraction materials should be continuously designed for low cost and effective isolation of volatile thiols, apart from maximising the potential of currently available extraction methods. For example, the potential of novel molecularly imprinted polymer SPME fibres for volatile analysis keeps growing [80], and it seems plausible that SPME fibre coatings could also be customised for volatile thiol extraction. The same can be suggested for SPEsorbent materials, given the recent example of an Ag\({}^{+}\) based SPE cartridge that has been proposed for volatile thiol analysis [28]. Regarding the future of chromatographic separation in the analysis of volatile thiols, emerging trends include the testing of novel stationary phases and new separation techniques. With respect to the stationary phases, new generation superficially porous silica LC columns have been made commercially available and reported for the separation of a variety analytes [81]. These columns are compatible with conventional HPLC instrumentation (including MS), and the chemistries of the stationary phases are similar to conventional C18 columns, but they offer faster and more efficient separation [81]. Other than new generation LC columns, there are also other stationary phases of potential interest. As an example, a polysaccharide-based chiral LC column has not only demonstrated good analytical performance for separation of thiol enantiomers, but it also revealed the possibility to simultaneously analyse other important achiral volatile thiols [41]. Alternative separation techniques should be also considered, besides improving separation through new columns.