Rapid and quantitative determination of total sterols of plant and animal origin in liver samples by gas chromatography

A simple and rapid method to quantify sterols by gas-chromatography (GC) in liver samples is described. The most usual methods to determine sterol content by GC in biological samples involve lipid extraction, saponification, extraction of non-saponifiables and their fractionation. This paper proposes a direct saponification of biological samples (liver) in order to save time and solvents. Samples were homogenised with ethanol, which contained a mixture of antioxidants, followed by a saponification step using KOH 1 N, extraction of non-saponificables and, finally, purification step using a SPE cartridge. Gas-chromatography analysis was performed using a ZB-1 (100% methylpolisiloxane) capillary column and an oven temperature program, which involves two rates from 245 to 290 degrees C. Analytes were identified by their relative retention time and by co-chromatography. Quantitative analysis was carried out by using 5 alpha-cholestane as internal standard (IS). Repeatability, recovery and linearity were determined. Values of repeatability (n = 8) in liver were [mean mu g/ 100 mg (RSD)]: for squalene [0.68 (12.99%)], for cholesterol [190.82 (2.34%)], for lathosterol [0.48 (3.05%)], for campesterol [3.90 (2.55%)] and for beta-sitosterol [0.27 (19.69%)]. In conclusion, this method offers interesting perspectives for the quantitative analysis of these sterols not only in liver, but also in other biological samples.