24 r s hydroxycholesterol d6

24S-Hydroxycholesterol [cholest-5-ene-3-beta,24S-diol], 25-hydroxycholesterol [cholest-5-ene-3-beta,25-diol], 27-hydroxycholesterol [cholest-5-ene-3beta,27-diol], 24(R/S)-hydroxycholesterol-d6 [26, 26, 26, 27, 27, 27-hexadeuterocholest-5-ene-3 beta,24-diol], 25-hydroxycholesterol-d6 [26, 26, 26, 27, 27, 27-hexadeuterocholest-5-ene-3 beta,25-diol] and 27-hydroxycholesterol-d6 [25, 26, 26, 26, 27, 27-hexadeuterocholest-5-ene-3 beta,27-diol] were obtained from Avanti Polar Lipids (Alabama, USA). 2-methyl-6-nitrobenzoic anhydride, 4-dimethylaminopyridine, picolinic acid, pyridine and trimethylamine were purchased from Sigma Aldrich Co. (St. Louis, USA). Phosphoric acid and potassium hydroxide were provided by Junsei (Tokyo, Japan). Distilled water was purified using a Milli-Q purification system (Millipore, Massachusetts, USA). High performance liquid chromatography (HPLC)-grade methanol, ethanol, hexane and 2-propanol were purchased from Burdick & Jackson (Ulsan, Korea).

All solvents and chemicals were HPLC grade. Methanol (CH3OH), ethanol (C2H5OH) and diethyl ether (CH3-CH2-O-CH2-CH3) were purchased from Fisher Scientific (USA), ammonium formate (HCOONH4) and formic acid (HCOOH) were purchased from Sigma Aldrich (St. Louis, MO). 24S-hydroxycholesterol and 27-hydroxycholesterol were purchased form Research Plus Inc. (Barnegat, NJ). Internal standard 24(R/S)-hydroxycholesterol (d6) [cholest-5-ene-3β, 24(R/S)-diol (d6)] was purchased from Avanti Polar Lipids (Alabaster, AL). Glass vials were purchased from Agilent Technologies, Inc. (Santa Clara, CA). Isotemp vacuum oven was purchased from Fisher Scientific (Model 285A, Pittsburgh, PA). Borosilicate-coated glass tubes and pipettes were used to reduce adhesion of sterols to plastic and glassware (Fisher Scientific, Pittsburgh, PA).