Simultaneous extraction, derivatization and clean-up of sterols from soil using accelerated solvent extraction

A one-step extraction, derivatization and clean-up technique for the determination of sterols in soil by accelerated solvent extraction (ASE) is presented. In this method, in situ derivatization of sterols using 99 % N, O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) + 1 % trimethylchlorosilane (TMCS) was carried out inside the extraction cell. The extracts were analyzed by gas chromatography with mass spectrometry detector (GC-MSD) and gas chromatography with flame ionization detector (GC-FID). The effects of solvent, sorbent and temperature on the in situ derivatization of sterols were investigated using Ottawa sand fortified at 50 ppm sterol mixture (cholestrol, stigmasterol and stigmastanol). The extraction performed using dichloromethane at extraction pressure of 1500 p.s.i, temperature 60 degree Celsius and static extraction time of 15 min gave recoveries from 87 to 96 %. The effect of several types of sorbents as on-line clean-up by inclusion of sorbents in the extraction cell on the extraction efficiencies were investigated using spiked soil sample. Increase in static extraction time significantly improved the recoveries of the analytes. The utilization of integrated extraction, derivatization and clean-up strategy simplify and shorten the sample preparation step in an analysis. (author)