Investigation of artefact formation during analysis of volatile sulphur compounds using solid phase microextraction (SPME)

The occurrence and origin of artefact formation during the analysis of volatile sulphur compounds in air by PDMS/Carboxen fibre were investigated. Among the studied compounds (hydrogen sulphide, carbon disulphide, diethyl sulphide, methyl ethyl sulphide, isopropanethiol, methanethiol, dimethyl sulphide, dimethyl disulphide, carbonyl sulphide), essentially mercaptans were shown to react to form the corresponding dimers. However, in the presence of several oxygenated and amines compounds which are common components of industrial effluents, no further artefact formation or reaction was noticed. Artefact formation was therefore considered to be independent of the sample matrix. Thermal oxidation occurring during the desorption step in the GC injection port was assessed. As metallic elements were previously suspected to catalyse the reaction, a specially deactivated SPME needle was tested, but no significant difference was noticed compared to the original needle. It was therefore assumed that metallic elements naturally present on Carboxen may act as catalysts. Similar results were obtained by using Carboxen in adsorbent tubes, as artefacts were increased by comparison with Tenax TA and molecular sieve 5A.