title: Measurement of urinary F(2)-isoprostanes by gas chromatography-mass spectrometry is confounded by interfering substances.
abstract: Analysis of F(2)-isoprostanes in urine using gas chromatography-mass spectrometry is confounded by the presence of endogenous compounds interfering with the internal standard, 15-F(2t)-IsoP-d(4) (m/z 573). Previous efforts to resolve the 15-F(2t)-IsoP-d(4) from co-eluting peaks with different solid phase extractions were unsuccessful. This study has now used a highly-deuterated, d(9)-analogue of the derivatization agent N,O-Bis(trimethyl-d(9)-silyl) trifluoroacetamide (BSTFA-d(9)) yielding trimethylsilyl ethers, but this was not successful in resolving the 15-F(2t)-IsoP-d(4) from co-eluting peaks. It was hypothesized that interfering peaks at m/z 573 could be the tetrahydro analogue of 15-F(2t)-IsoP. However, using an authentic standard showed the interfering peaks are not due to this metabolite. In subsequent experiments good resolution was shown of the 15-F(2t)-IsoP peak using 8-F(2t)-IsoP-d(4) (m/z 573) as the internal standard. These data show that care must be taken when using GC-MS for quantitation of F(2)-IsoPs to prevent interfering substances affecting the results.
authors.affiliation: School of Medicine and Pharmacology, Royal Perth Hospital Unit, University of Western Australia and the Cardiovascular Research Center, Perth, Australia. emilie.mas@uwa.edu.au
authors.forename: Emilie
authors.initials: E
authors.lastname: Mas
authors.forename: Anne
authors.initials: A
authors.lastname: Barden
authors.forename: Thierry
authors.initials: T
authors.lastname: Durand
authors.forename: Jean-Marie
authors.initials: JM
authors.lastname: Galano
authors.forename: Kevin D
authors.initials: KD
authors.lastname: Croft
authors.forename: Trevor A
authors.initials: TA
authors.lastname: Mori
mesh_terms: D028441:F2-Isoprostanes / Q000138:chemical synthesis / Q000737:chemistry / Q000652:urine*; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D008968:Molecular Conformation; D012016:Reference Values
chemical_list: D028441:F2-Isoprostanes