Determination of Existing and Potential Dimethyl Sulphide in Red Wines by Gas Chromatography Atomic Emission Spectroscopy

The activity of micro-organisms in food and beverages can produce dimethylsulphide (DMS), characteristic of composition and condition. DMS and potential DMS derived from precursor compounds in red wines have been analysed by gas chromatography with the atomic emission detector (GC-AED). The AED was found to be a specific and sensitive instrument for volatile sulphur compound analysis which allowed confirmation of sulphur response by observation of its characteristic emission spectra. DMS present in wines was purged from diluted samples to an adsorbent composed of gold-coated glass wool. This was thermally desorbed to a valving and cryogenic trap system coupled to the GC-AED which also provided permeated methylethylsulphide as an internal standard. This configuration was also suitable for the analysis of CS2present in the wines. For DMS a coefficient of variation of 3% was obtained from replicate analyses of wine samples between 30 and 200 μg/L, with a limit of detection of 1 μg/L using 1/1000 diluted samples. DMS precursor was assessed using 0.5, 1.0 and 2.0 M NaOH at 80°C to liberate DMS. Different amounts of DMS were released from the various samples using the three alkaline strengths, necessitating that a standard set of conditions be adhered to in order to gauge the potential for DMS release during storage.