Determination of secondary metabolites from fungi and lichens in samples of settled dust taken from indoor environments

The current study aimed to apply an optimized and validated LC-MS/MS “dilute and shoot” method for the determination of more than 1000 different fungal and bacterial metabolites in settled dust samples. The method was validated in the laboratory according to the guidelines established in the Directorate General for Health and Consumer Affairs of the European Commission (SANCO) document No. 12495/2011.The analysis was performed on dust samples collected from buildings in Finland. Extraction was performed using the extraction solvent: Acetonitrile/Water/FormicAcid (79:20:1, v/v/v). The extracts were diluted with the dilution solvent: Acetonitrile/Water/FormicAcid (20:79:1, v/v/v) subsequently injected into the LC-MS/MS system without any further pre-treatment. Satisfactory results as regards extraction efficiency and repeatability were obtained covering the mainly known mycotoxins groups produced by Aspergillus, Fusarium and Penicillium species, the emerging analytes produced by the other Fusarium and Alternaria species as well as a group of metabolites produced by lichens that were not described elsewhere in previous publications in the Mediterranean area. For those metabolites, the number of positive samples as well as the related concentrations exceeded those of fungal metabolites by far. In fact, these results encourage a continuous control to assess a potential occurrence of secondary metabolites in the buildings and to prevent health problems.