Development of a Gas Chromatography–Mass Spectrometry Method for the Determination of Ergosterol in Forest Soils

ABSTRACT Ergosterol is a sterol compound present in fungal cell membranes and is used as a biomarker to measure fungal biomass. Therefore, an accurate analytical method is essential to quantify the presence of ergosterol in any soil type, regardless of its physicochemical characteristics or environmental conditions. The main objective of our study was to optimise and validate an analytical method for the assessment of total ergosterol content in soil. Different parameters were evaluated during the optimisation of the method to extract ergosterol from agricultural and forest soils. The accuracy of the method was evaluated by the recovery of ergosterol from soil spiked at two levels, resulting in good recoveries for both types of soil. Gas chromatography–mass spectrometry was used to analyse soil extracts without requiring a derivatization step. This simplifies the procedure and avoids the use of toxic reagents. The analytical method was applied to determine ergosterol in forest soils taken at two depths (0–5 cm and 5–10 cm). Significant differences in the concentrations of ergosterol in the top and deeper layers of soil were observed. The quantity of ergosterol in the upper soil layer ranged from 3.0 to 29.9 mg/kg dry weight, whereas in the deeper layer of soil, it ranged from 0.5 to 4.8 mg/kg dry weight. The principal component analysis performed between ergosterol concentration and soil characteristics at both depths displayed a correlation between ergosterol and organic matter.