The n-alkylcyclohexanes are poorly evaluated in biodegradation studies of Brazilian petroleum samples. In this context, this work aimed to use the homologue series of alkylcyclohexanes to assess extend of biodegradation of 26 petroleum samples from five Brazilian sedimentary basins, analyzed by gas chromatography coupled to mass spectrometry. The n-alkylcyclohexanes compounds were detected in all samples, with a distribution similar to the n-alkane profile, in which their abundance decreasing with increasing of the biodegradation extent. Based on this, it was suggested the use of the new parameter H30/DC together with the H30/AC already proposed, calculated by the ratio between C30 hopane to the dodecyl-cyclohexane, to assess biodegradation level according Peter and Moldowan scale (PM scale). In addition, it was observed an increasing in the relative abundance of DBE 2 from class O2, analyzed by ESI(-) FT-ICR MS, mainly due to the formation of monocyclic acids with biodegradation, which correlates with the decrease of n-alkylcyclohexanes, a possible precursor of these acids.
Keywords:
petroleum; biodegradation; n-alkylcyclohexanes; GC-MS; petroleomics
