Identification of Odor-Active Organic Sulfur Compounds in Gypsum Products

Gypsum is widely used in building products, e.g., as drywall, stucco or constituent in mortar, because it is easy to handle and it is assigned creating a good indoor air quality. Odor analysis of a gypsum product with a sulfurous off-odor by means of gas chromatography-olfactometry compared to two unobtrusive commercial gypsum products revealed - apart from typical odor compounds previously found in building products like aldehydes, ketones and acids - various organic sulfur compounds as odorants at very small concentrations (<< 1 mu g/m(3)) not allowing structural identification. Gypsum deposits naturally contain impurities and elemental sulfur, which can react in nature due to tectonic pressure and temperature or during production with organic compounds, e.g., from beater additives, to form organic sulfur compounds. Odor analysis of a gypsum raw material and its semi-processed product from a Chinese deposit with a very intense sulfurous off-odor revealed high concentrations of organic sulfur compounds, which were identical in analytical, chromatographic and sensory properties to the unidentified sulfur compounds of the commercial products and are therefore suitable for structural identification of those unknowns. In this way, a number of sulfides, disulfides, thiols and aromatic sulfur compounds could be identified as contributing to the odor of gypsum products.