Occurrence of extended tetracyclic polyprenoid series in crude oils

Abstract

A homologous series of tetracyclic polyprenanes from C24 to C41 was identified in crude oils from Espírito Santo Basin (Brazil) by comprehensive two-dimensional gas chromatography–time-of-flight mass spectrometry (GC×GC–TOFMS) and gas chromatography–tandem mass spectrometry (GC–MS-MS) analyses. These products were separately characterized by elution order in first- and second-dimension retention times (1tR and 2tR, respectively), time-of-flight mass spectra (TOFMS), MRM chromatograms, product ion spectra including diagnostic ions at m/z 191, m/z 259 and m/z 149 + 14n (n = 0–17), the latter a key mass fragment for the evaluation of side chain extension at the C-18 position in tetracyclic polyprenoids. The tetracyclic compounds were thus identified as scalarane-like structures related to abundant C30 tetracyclic polyprenoids, an important indicator of input from fresh to brackish water paleoenvironments.