title: Determination of isotopic enrichments of [1-13C]homocysteine, [1-13C]methionine and [2H3-methyl-1-13C]methionine in human plasma by gas chromatography-negative chemical ionization mass spectrometry.
abstract: We describe a reliable method for the simultaneous determination of isotopic enrichments of [1-13C]homocysteine, [1-13C]methionine and [2H3-methyl-1-13C]methionine in human plasma. Accurate [1-13C]homocysteine calibration standards were prepared by chemical conversion via thiolactonisation of [1-13C]methionine standards. Based upon anion-exchange chromatography, (di)acetyl-3,5-bis-trifluoromethylbenzyl derivatives, preparation of accurate calibration curves and gas chromatography-negative chemical ionization mass spectrometry, isotopic enrichments in human plasma could be determined with TTR (%) <+/-0.2% (N=3) for [1-13C]homocysteine (enrichment range 0-8%), [1-13C]methionine (enrichment range 0-3%) and [2H3-methyl-1-13C]methionine (enrichment range 0-12%). The method was applied in a [2H3-methyl-1-13C]methionine tracer infusion study in a biological model.
authors.affiliation: Department of Clinical Chemistry, University Hospital Vrije Universiteit, Amsterdam, The Netherlands. w.kulik@azvu.nl
authors.forename: W
authors.initials: W
authors.lastname: Kulik
authors.forename: R M
authors.initials: RM
authors.lastname: Kok
authors.forename: K
authors.initials: K
authors.lastname: de Meer
authors.forename: C
authors.initials: C
authors.lastname: Jakobs
mesh_terms: D002247:Carbon Isotopes; D003903:Deuterium; D004355:Drug Stability; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D006710:Homocysteine / Q000097:blood*; D006801:Humans; D007700:Kinetics; D008715:Methionine / Q000031:analogs & derivatives* / Q000097:blood* / Q000493:pharmacokinetics; D008745:Methylation; D011786:Quality Control; D012680:Sensitivity and Specificity
chemical_list: D002247:Carbon Isotopes; D006710:Homocysteine; D008715:Methionine; D003903:Deuterium; C038344:methionine methyl ester