Extraction and purification of free cholesterol from some egg-containing food by on-line supercritical fluid extraction – solid-phase extraction

 Two methods for the extraction and determination of free cholesterol in some egg-containing food samples were compared: the classical Soxhlet method and a supercritical carbon dioxide extraction (at 338 bar and 40  °C) coupled on-line with solid-phase extraction (SPE with a solid trap packed with an ODS stationary phase). Egg noodles, biscuits and sweet snacks were homogenised and added to the internal standard and anhydrous sodium sulphate. Part of each sample was extracted by on-line supercritical fluid extraction – solid-phase extraction (SFE-SPE) and the remaining part was extracted by the classical method using petroleum ether. A further purification after the Soxhlet extraction was performed by SPE. Free cholesterol was determined in both the off-line Soxhlet-SPE fraction and the on-line SFE-SPE extract with capillary gas chromatography after silylation. The two extraction methods gave similar results. However, on-line SFE-SPE represents a valid alternative to the Soxhlet method because it shows important advantages, such as a short analysis time and low solvent consumption.