Stability of Cholesterol; Cholesterol-5β,6β-Epoxide; Cholesta-3,5-Dien-7-One, and 5α-Cholestane in Solution During Short-Term Storage

Because cholesterol and its oxide products (COPs) are used as standards during analysis, their stability and autoxidation were assessed under typical storage conditions. Individual toluene solutions of cholesterol; cholesterol5β, 6β-epoxide; cholesta-3,5-dien-7-one; and 5α-cholestane were prepared and aliquots were stored at 23 ± 2°C, 4°C, and -20°C for 7 days. Samples were removed from storage, dried under nitrogen, derivatized and analyzed using gas chromatography-flame ionization detection and gas chromatography-mass spectrometry. β-sistosterol and 5-colest-ene-7-one were found to be a suitable recovery internal standard and an instrument internal standard, respectively. All compounds in solution had no detectable artifact generation during 7 days of storage; thus, they were stable. Storage temperatures of 23 ± 2°C, 4°C, and -20°C did not affect stability. Chromatograms revealed contaminants and other peaks likely associated with incomplete derivatization of some compounds; potential causes for the unusual lack of derivitization are discussed.