Analysis of trimethylsilylperoxy derivatives of thermally labile hydroperoxides by gas chromatography-mass spectrometry.

Qualitative and quantitative determinations of hydroperoxides are of central importance in many areas of biochemical research, but analysis of intact hydroperoxides by capillary gas chromatography-mass spectrometry (GC-MS) generally has not been possible due to the thermal instability of these compounds. It is demonstrated here that structurally diverse hydroperoxides can be converted to trimethylsilyl (TMS) peroxides and analyzed by GC-MS without significant thermal decomposition. The hydroperoxides investigated in this report include cumyl hydroperoxide, 2-phenylethylhydroperoxide, 13-hydroperoxy-octadeca-9,11-dienoic acid, 2,6-di-tert-butyl-4-hydroperoxy-4-methylcyclohexadienone (BHTOOH), and 2,4,6-trimeth-yl-4-hydroperoxycyclohexadienone (TMPOOH). A representative peracid, 3-chloroperoxybenzoic acid, was successfully analyzed as its TMS peroxyester. Chromatographic and mass spectral characteristics of the TMS peroxides and their corresponding TMS ethers were obtained and compared with thermospray HPLC-MS data for underivatized hydroperoxides. The utility of the GC-MS assay for quantitating low levels of hydroperoxides in biological matrices was demonstrated by measuring BHTOOH and TMPOOH formed during the NADPH-dependent oxidation of alkylated phenols by rat liver microsomes. Overall, the results demonstrate that the advantages of GC-MS analysis (i.e., high chromatographic resolution, quantitative precision, high sensitivity, and the acquisition of structural information) can be applied successfully to intact hydroperoxides following trimethylsilylation.