A novel approach to the analysis of spin-trapped free radicals using dimethyl sulfoxide and gas chromatography - mass spectrometry (GC-MS) with both solvent extraction and headspace solid phase microextraction (HS-SPME)

In this study, we have utilized a novel strategy based upon the use of dimethyl sulfoxide (DMSO) and gas chromatography-mass spectrometry (GC-MS) for the detection and identification of spin-trapped free radicals. Hydroxymethyl (CH₂OH) radicals, generated by Fenton-type chemistry, have been trapped by N-tert-butyl-α-phenylnitrone (PBN) or one of its derivatives in the presence of DMSO to form a 1,3-diadduct [PBN-(CH₂OH)(CH₃)], which may be detected directly in the reaction mixture following chloroform extraction or in the reaction vial headspace by sampling with SPME. Separation and identification have been carried out by capillary gas chromatography coupled to electron-ionization mass spectrometry (EI-MS). The results demonstrate that using DMSO aids GC-MS analysis of spin-trapped free radicals via the formation of radical-methyl di-adducts that are sufficiently volatile to be sampled both in the headspace or by an extracting solvent without the need for a derivatization step using silylating agents.