Analysis of volatile sulphur compounds in breath by gas chromatography–mass spectrometry using a three-stage cryogenic trapping preconcentration system

A method for the determination of trace volatile sulphur compounds (VSCs) including methanethiol, dimethyl sulfide (DMS) and dimethyl disulfide (DMDS) at low ppbv (volume/volume) in breath has been developed using a large volume preconcentration technique prior to capillary GC–MS analysis. The breath sample was collected in a 6-l fused-silica-lined stainless steel canister and introduced into the three-stage cryogenic trapping preconcentration system by GC–MS in the total ion monitoring (scan) mode. The water condensation effect of breath sample inside the canister, which is due to the difference between human body temperature and laboratory temperature, was examined. The condensed water in the fused-silica-lined canister at 24°C did not affect the recoveries of VSCs within 12 h. As this three-stage cryogenic trapping preconcentration technique made it possible to remove excess water {relative humidity (RH) >95%} and carbon dioxide (3.8%) without loss of the VSCs, more than 400 ml of the breath sample could be concentrated. The detection limits of methanethiol, DMS and DMDS in a breath sample using this method were 0.13, 0.09 and 0.15 ppbv, respectively.