EXTRACTION OF ERGOSTEROL FROM PEATY SOILS AND DETERMINATION BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

The ergosterol content of soil can be used as an indicator of fungal a ctivity. A method has been developed for the extraction and determinat ion of ergosterol in organic soils, as part of a study to assess the c orrelation between fungal activity and the sequestration of metal poll utants. The moisture content of the soil affected the extraction proce ss. Four consecutive extractions with methanol removed >95% of the erg osterol that can be obtained from the fresh sample (63% moisture) by e xhaustive extraction. By freeze drying the soils prior to extraction ( a) up to 35% more ergosterol was extracted after a single extraction, (b) >90% of the recoverable ergosterol was collected in two extraction s and (c) the repeatability of the extraction was improved. Storage of soil extracts in the absence of light prevents degradation of ergoste rol. A previously reported method for determination of ergosterol by H PLC has been improved by modification of the eluant composition. With 46% methanol/46% acetonitrile/8% dichloromethane, ergosterol was elute d with good resolution approximately 8 min after injection of 20 mul o f the extract. The detection limit of the HPLC method was 0.5 mug/ml e rgosterol, equivalent to 0.06 mug/g in 25 g fresh soil. Changes in erg osterol contents of peaty soil treated with fungicide, and in samples of the peaty podzol and a humus iron podzol in the vicinity of fungal fruiting bodies, have been determined.