干旱区生态环境知识资源中心

F-2-isoprostanes (F-2-iPs), established markers of oxidative stress, exist as four sets of regioisomers. Simultaneous and specific determination of F-2-iPs can be achieved by liquid chromatography-tandem mass spectrometry (LC-MS/MS). We developed novel methods for urine sample preparation and HFLC to control matrix-related ion suppression effects in the LC-MS/MS analysis of F-2-iPs. A selective solid-phase extraction (SPE) wash protocol was developed with an Oasis HLB (hydrophilic-lipophilic balance) SPE cartridge using an elution profile of [H-3]8-iso-prostaglandin (PG)F-2 alpha (iPF(2 alpha)-III) when the methanol concentration was increased under acidic, neutral, and base wash conditions. A multidimensional (MD)-SPE method that incorporated size exclusion, reverse-phase chromatography, and normal-phase chromatography was developed using an Oasis HLB SPE cartridge and an HLB mu Elution SPE plate. Average extraction recoveries of the deuterated internal standards of iPF(2 alpha)-III and iPF(2 alpha)-VI were 62 +/- 8% and 60 +/- 10%. A buffer-free HPLC method for the separation of F-2-iP isomers was developed on base-deactivated C8 columns. Average matrix effects for iPF(2 alpha)-III and iPF(2 alpha)-VI were 95 +/- 6% and 103 +/- 5%. The clean extraction of urine F-2-iPs using MD-SPE and the separation of F-2-iP isomers using a novel HPLC method did not cause apparent ion suppression in the analysis of iPF(2 alpha)-III and iPF(2 alpha)-VI using LC-MS/MS. These findings should be useful for establishing a routine LC-MS/MS method for the analysis of F-2-iPs.,