Use of Gas Chromatography/Ion‐trap Tandem Mass Spectrometry for the Determination of Chemical Markers of Microorganisms in Organic Dust

Gas chromatography/tandem mass spectrometry (GC/MS/MS) using an ion-trap instrument was applied for the determination of ergosterol, muramic acid and 3-hydroxy fatty acids with 10-18 carbon atoms in samples of organic dust. These substances were used as chemical markers to measure fungal biomass, bacterial peptidoglycan and Gram-negative bacterial lipopolysaccharide, respectively. It was found that detection limits attained with GC/MS/MS were comparable to those reached with conventional quadrupole GC/MS analysis using selected-ion monitoring, since all markers, analysed as trimethylsilyl derivatives (the fatty acids after methylation of the carboxyl group), were detectable in the low-picogram range (injected amounts). GC/MS/MS, however, gave results that were easier to interpret owing to the superior detection specificity. Ion trap tandem MS is a convenient technique that should be very useful for the determination of microbial substances in environmental samples, including organic dust.