Determination of Volatile Sulfur Compounds in Air and other Gas Matrices : Development and Applications of Solid-Phase Microextraction

Abstract: Volatile sulphur compounds (VSCs) are frequently emitted during bioindustrial activities, such as production of biogas, sewage treatment, landfilling, pulpmilling, and the slaughtering of animals and meat processing. VSCs are reactive and malodorous, and they can also be detrimental to human health, therefore it is of great interest to be able to analyze these compounds.However, the standard techniques that are now available for determination of VSCs entail detection limits that in some cases exceed the odor thresholds, and, what is more, they require the use of solvents and toxic reagents. In addition, a single standard method does not exist that can be used to analyze all the VSCs that are most often associated with bioindustrial processes.In the present studies, a technique based on solid-phase microextraction (SPME) was developed for analysis of the VSCs that are commonly found in the bioindustry. The method could even be applied to very complex gas matrices representing point-source emissions of these compounds in amounts below their odor thresholds. Furthermore, the procedure constitutes an improvement compared to the other techniques employed to determine VSCs, because SPME is less time-consuming, it does not require the use of solvents or other chemicals, and it can extract all the compounds simultaneously. The potential of applying SPME for time-weighted average sampling of VSCs was also investigated. These experiments showed that the connnercially available fiber coating with the highest affmity for VSCs (i.e., Carboxen-polydimethylsiloxane)could achieve accurate determination of dimethyldisulfide, whereas use of thatcoating to collect the other compounds was highly influenced by externalparameters that are subject to variation. This work also included investigationsof several important aspects of SPME analysis of VSCs, such as the choice offiber coating, artifact formation, and the impact of various parameters on theextraction.The current results demonstrate that the SPME methodology that was developed can be used to determine VSCs in different matrices and contexts within the bioindustry. More precisely, the technique was successfully employed for the following purposes: to determine background levels ofVSCs to which workers were exposed; to monitor VSC emissions during the biogas process; to supervise the quality of produced biogas; to investigate the efficiency of processes used for abatement of VSCs; and to ascertain the cause of odor problems.