Quantitative analysis of volatile sulfur compounds in beer using a membrane extraction interface

Improved quantitation of volatile sulfur compounds in beer using membrane extraction is demonstrated. The membrane consists of a silicone tube (300 mm x 0.29 mm i.d. x 0.6 mm o.d.). The tube, purged with helium for flame photometric detection or with nitrogen for sulfur chemiluminescence detection is placed directly in the beer, and the sulfur compounds that permeate through the walls of the tube are collected cryogenically and thermally desorbed onto a capillary gas chromatographic column for analysis. Replicate analysis of a single sample shows a coefficient of variation (CV) of <5%, whereas replicate analysis of multiple samples from the same batch gave a CV of approximately 10%. Recovery of sulfur compounds is linear over the range normally expected in beer. The use of the technique to investigate changes in sulfur compounds in beer over time is also discussed.