Ergosterol extraction and detection from a variety of environmental matrices

B. Verma, J. V. Headley, R. D. Robarts, K. M. Peru and N. Christofi

Abstract

The presence and biomass of fungi can be measured indirectly by the detection of ergosterol, a compound generally specific to the cell membranes of fungi. Ergosterol is most often detected using high-pressure liquid chromatography with a UV detector (HPLC-UV). We tested a variety of techniques for the extraction of ergosterol and conducted a general survey of different matrices in an aquatic environment. More importantly, data acquired from the HPLC-UV system was further confirmed with liquid chromatography atmospheric pressure chemical ionisation tandem mass spectrometry (LC/APCI/MS/MS) for the presence of ergosterol. Though other procedures gave overall better recoveries of ergosterol extracted, the optimum extraction method proved to be a previously established one of saponification followed by toluene extraction. This method resulted in a relatively clean sample with ergosterol recoveries of above 90%. Ergosterol was widely distributed at ppm levels in matrices of decaying willow leaves, Scirpus stems (living and dead) and sediment collected at the water sediment interface. In the case of water samples, the HPLC-UV system falsely indicated the presence of ergosterol thus pointing to the need for the more selective mass spectral confirmation on samples where chromatographic co-elution is a problem.