Rapid quantification of free and esterified phytosterols in human serum using APPI-LC-MS/MS

A novel analytical platform based on liquid chromatography and tandem mass spectrometry using atmospheric pressure photoionization was applied for the simultaneous quantification of free and esterified β-sitosterol, campesterol, brassicasterol, and stigmasterol. The total time for sample pretreatment and analysis could be reduced from ∼3 h [gas chromatography-mass spectrometry (GC-MS)] to 15 min. The detection limits of the different phytosterols ranged between 0.25 and 0.68 μg/l. Linear ranges were between 1 and 1,000 μg/l. The within-run and between-run variabilities ranged between 1.4% and 9.9%. The analytical sensitivity was at least 150-fold higher compared with GC-MS.Our new method allows a rapid and simultaneous determination of free and esterified phytosterols in serum.