title: Isolation and quantification of cholesterol oxides in dairy products by selected ion monitoring mass spectrometry.
abstract: A method for isolation, detection and quantification of cholesterol oxidation products based on solid phase extraction in combination with preparative HPLC and gas chromatography-mass spectrometry selected ion monitoring has been developed for dairy products. The isolation procedure had a high recovery and artifact formation was minimal, as shown by isotope labelling. The limits of detection ranged from 0.3 to 35 pg/microliters of the isomeric forms of 7-hydroxycholesterol, 20 alpha-hydroxycholesterol, the isomeric forms of cholesterol-5,6-epoxides, cholestanetriol, 25-hydroxycholesterol and 7-ketocholesterol corresponding to a limit of quantification of 2-6 ng oxysterol/g lipid in the dairy product, depending on the nature of the cholesterol oxidation product.
authors.affiliation: Department of Dairy and Food Science, Royal Veterinary and Agricultural University, Frederiksberg, Denmark.
authors.forename: J H
authors.initials: JH
authors.lastname: Nielsen
authors.forename: C E
authors.initials: CE
authors.lastname: Olsen
authors.forename: C
authors.initials: C
authors.lastname: Duedahl
authors.forename: L H
authors.initials: LH
authors.lastname: Skibsted
mesh_terms: D002777:Cholestanols / Q000032:analysis; D002784:Cholesterol / Q000031:analogs & derivatives / Q000032:analysis*; D002788:Cholesterol Esters / Q000032:analysis; D002851:Chromatography, High Pressure Liquid; D003611:Dairy Products / Q000032:analysis*; D008401:Gas Chromatography-Mass Spectrometry; D006888:Hydroxycholesterols / Q000032:analysis; D007653:Ketocholesterols / Q000032:analysis; D013058:Mass Spectrometry / Q000379:methods*; D010084:Oxidation-Reduction; D010087:Oxides / Q000032:analysis*; D014280:Triglycerides / Q000032:analysis
chemical_list: D002777:Cholestanols; D002788:Cholesterol Esters; D006888:Hydroxycholesterols; D007653:Ketocholesterols; D010087:Oxides; D014280:Triglycerides; C002415:cholesterol alpha-oxide; C025813:20-hydroxycholesterol; C007997:25-hydroxycholesterol; D002784:Cholesterol; C003001:7-ketocholesterol