A green liquid chromatography-tandem mass spectrometry method for the simultaneous analysis of volatile thiols and their precursors in oenological samples

Improvements to the quantification of three white wine impact odorants 3-sulfanylhexan-1-ol, 3-sulfanylhexyl acetate, and 4-sulfanyl-4-methylpentan-2-one, and the non-volatile precursors from which they are released during fermentation, is of great interest to the wine science community. Recent reports of a "Quick, Easy, Cheap, Effective, Rugged and Safe" (QuEChERS) based method for the concurrent analysis of these thiols and their precursors via liquid chromatography tandem mass spectrometry (LC-MS/MS) has enabled the development of far simpler methods, as well as aligning these analyses with principles of green analytical chemistry. This current work reports the development and validation of a QuEChERS based LC-MS/MS method utilising a safer derivatising agent, 4,4'-dithiodipyridine, while greatly minimising the reagents involved and waste produced. We demonstrate that this new method compares favourably to the previously reported method with repeatability of 0.2-1.3%RSD and 0.4-5.2%RSD for precursors and free thiols. Further, the commercially available internal standard, 1-hexanethiol, used in previous analytical methods was compared to stable isotope labelled analogues of the analytes, with results suggesting that it may not be a reliable internal standard.