Highly sensitive analysis of cholesterol and sitosterol in foods and human biosamples by liquid chromatography with fluorescence detection

A simple and sensitive method is described for the quantitative analysis of important animal and plant sterols (cholesterol and sitosterol) by liquid chromatography with fluorimetric detection. The method is based on the derivatization of cholesterol and sitosterol with a fluorescent reagent (naproxen acyl chloride) in toluene. The resulting derivatives were isocratically separated on a C8 column with a mixed solvent of methanol–isopropanol–water (90:5:5, v/v) as a mobile phase and monitored with a fluorimetric detector (excitation 231 nm and emission 352 nm). The linear range for the quantitation of cholesterol or sitosterol was 0.1–2.0 μM with a detection limit (S/N = 3 with 10 μl injected) of about 25 nM. Recoveries of cholesterol spiked in milk (n = 5) ranged over 99–104% with relative standard deviations (RSD) less than 6.0%. Application of the method to the analysis of cholesterol or sitosterol in milk, saliva and urine proved simple and feasible.