Preliminary exploration of polysulfide detection in wine using fluorescent probe SSP4 and A-TEEM spectroscopy

Polysulfides have emerged as a novel class of sulfur compounds in wine that continue to be explored and characterised, but analytical challenges still remain. The fluorescent probe SSP4, developed for sulfane sulfur detection in biological systems, was preliminarily evaluated for its potential applicability to wine analysis. Glutathione trisulfide (GS-S-SG) was employed as a standard polysulfide, and the reaction with SSP4 was monitored in phosphate buffer and wine matrices using absorbance-transmittance and fluorescence excitation-emission matrix (A-TEEM) spectroscopy. The SSP4 probe produced a strong fluorescence signal with excitation at 495 nm and emission at 515 nm in buffer solution. Excitation maxima shifts detected in wine were suggestive of solution composition effects upon probe activation. GS-S-SG added to diluted or undiluted wine resulted in variable responses, indicating the presence of endogenous polysulfide or sulfane sulfur intermediates in wine. These initial findings demonstrated the feasibility of SSP4-based fluorescence detection for wine polysulfides, with a need to address matrix-related factors potentially as a consequence of inner filter effects or endogenous polysulfide equilibria. Further investigation of probe activation conditions is therefore warranted to enable quantitative applications in wine.