Nalophan bags are commonly used for air sampling and especially for odour analysis. Even if olfactometric measurement must be carried out within maximum 30 hours after sampling, the question of potential sample evolution is always present. This study illustrates the behaviour of selected sulphur compounds in Nalophan bags from filling to analysis (over a period up to 100 hours).
Select compounds were hydrogen sulphide, carbon disulphide, methyl mercaptan, ethyl mercaptan, dimethyl sulphide, diethyl sulphide and dimethyl disulphide and tested at high concentration level (in a range of 3900 to 1800 ppb each) to facilitate their direct and quick measurement by gas chromatography with flame photometric detector. The chemical analysis shows losses by adsorption and by diffusion depending on time and other conditions. Even if the variation seems limited during the first hours, the evolution shows that the need for a better film is real.