Sterols in soil organic matter of sandy arable soils: Quantification using mass spectrometry and their relation to mineralizability of soil organic N

Lately, a significant negative correlation between proportions of the compound class of sterols from pyrolysis-field ionization mass spectrometry (Py-FIMS) and net N mineralizability of soil organic N was found. However, main plant sterols (?-Sitosterol, Stigmasterol, and Campesterol) cannot be clearly verified and quantified with Py-FIMS, and there are only very few studies on measuring concentrations in soils. Thus, the objective was the extraction, identification and quantification of typical plant sterols and their relation to net N mineralization rates. The three sterols were identified and quantified in lipid extracts (Soxhlet procedure) using gas chromatography - mass spectrometry (GC-MS). Concentrations were similar to few other available studies, but concentrations of the three sterols were not significantly correlated with net N mineralizability. As quantification was difficult due to co-elution, further optimization of the methodology is necessary. In addition, the underlying mechanisms also need to be clarified.