Impact of Saturation Effects during Dynamic Olfactometry on Low-Concentration Environmental Odour Samples

摘要

Environmental odour samples are often comprised of complex mixtures of compounds with diverse chemicalproperties and key odorants can be present at concentration levels in the low ppb range. This complicatesaccurate odour evaluations as adsorption to the inner walls of sampling equipment may significantly alter thechemical composition of the sample, even when the adsorption capacity is low. In the present study, thesignificance of saturation effects in dynamic Olfactometry on the recovery of single compounds in the low ppbrange and the impact on the chemical composition of odour samples typical for livestock houses is evaluated.The results are based on extensive measurements of three olfactometers obtained from accredited odourlaboratories, i.e. a TO8, a glass-tube olfactometer and a dilution system based on a mass flow controller. Theodorants include hydrogen sulphide, methanethiol, dimethyl sulphide, acetic acid, butanoic acid, propanoicacid, 3-methylbutanoic acid, 4-methylphenol, and trimethylamine. Furthermore, n-butanol, the reference gasaccording to the European standard, was included. All measurements were performed in real time with highsensitivity Proton Transfer Reaction Mass Spectrometry (PTR-MS). The results show that several keyodorants, including 4-methylphenol, trimethylamine and some carboxylic acids, were affected by surfaceadsorption to an extent, which could likely alter the outcome of odour measurements. Hence, it isrecommended to carefully consider olfactometer configuration and compound recovery for this type of odoursamples.