We describe a highly sensitive and specific method for the quantification of key regulatory
oxysterols in biological samples. This method is based upon a stable isotope dilution
technique by liquid chromatography-tandem mass spectrometry (LC-MS/MS). After alkaline
hydrolysis of human serum (5 μl) or rat liver microsomes (1 mg protein), oxysterols were
extracted, derivatized into picolinyl esters, and analyzed by LC-MS/MS using the
electrospray ionization mode. The detection limits of the picolinyl esters of 4β …