Determination of ergosterol on mouldy building materials using isotope dilution and gas chromatography–tandem mass spectrometry

Ergosterol content of building materials was quantified using gas chromatography–tandem mass spectrometry (GC–MS–MS) in an ion trap with external ionisation. Hydrolysing the samples by classic extraction at 85°C for 90 min in vials was faster, more precise and safer than microwave assisted extraction. [4-2H2]ergosterol was synthesised and used as internal standard, giving method standard deviation of 5–10% from 10 to 30 ng to 10–15 μg ergosterol in the sample. The use of GC–MS–MS meant that no solid-phase extraction clean-up was needed, so one person could easily prepare 40–80 samples per day.