Dual stir bar sorptive extraction using conventional and solvent-assisted approaches including in-situ derivatization followed by thermal desorption and gas chromatography–tandem mass spectrometry for analysis of polyfunctional thiols in white wine samples

A new method, based on the combination of two sorptive extraction methods, namely stir bar sorptive extraction (SBSE) and solvent-assisted stir bar sorptive extraction (SA-SBSE), was developed for the quantitative determination of ultra-trace levels of polyfunctional thiols in white wine. Extraction of 4-methyl-4-sulfanyl-pentan-2-one (4-MSP), 3-sulfanylhexan-1-ol (3-SH) and 2-furylmethanethiol (2-FMT) is performed by SA-SBSE combined with in-situ derivatization using ethylpropiolate (ETP), while 3-sulfanylhexyl acetate (3-SHA) is simultaneously extracted in parallel using SBSE, without derivatization. Analysis is performed by thermal desorption in combination with GC-MS/MS operated in selected reaction monitoring (SRM) mode. All four target solutes could be detected in a single GC-MS/MS run at levels below the odor detection threshold (ODT) of the solutes (LODs: 0.20 ng/L for 4-MSP, 2.8 ng/L for 3-SH, 0.27 ng/L for 3-SHA and 0.11 ng/L for 2-FMT). The method could be successfully applied to a set of white wine samples, showing significant differences in polyfunctional thiol concentrations between samples.