Control of matrix effects in the analysis of urinary F2-isoprostanes using novel multidimensional solid-phase extraction and LC-MS/MS

F2-isoprostanes (F2-iPs), established markers of oxidative stress, exist as four sets of regioisomers. Simultaneous and specific determination of F2-iPs can be achieved by liquid chromatography-tandem mass spectrometry (LC-MS/MS). We developed novel methods for urine sample preparation and HPLC to control matrix-related ion suppression effects in the LC-MS/MS analysis of F2-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 [3H]8-iso-prostaglandin (PG)F2α (iPF2α-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 μElution SPE plate. Average extraction recoveries of the deuterated internal standards of iPF2α-III and iPF2α-VI were 62 ± 8% and 60 ± 10%. A buffer-free HPLC method for the separation of F2-iP isomers was developed on base-deactivated C8 columns. Average matrix effects for iPF2α-III and iPF2α-VI were 95 ± 6% and 103 ± 5%. The clean extraction of urine F2-iPs using MD-SPE and the separation of F2-iP isomers using a novel HPLC method did not cause apparent ion suppression in the analysis of iPF2α-III and iPF2α-VI using LC-MS/MS. These findings should be useful for establishing a routine LC-MS/MS method for the analysis of F2-iPs.

Abstract licence: CC BY-NC-ND

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