Characterisation of the ruthenium tetroxide oxidation products from the aromatic unresolved complex mixture of a biodegraded crude oil

The monoaromatic, diaromatic and triaromatic fractions of a biodegraded cru de oil were oxidised using ruthenium tetroxide to cleave the alkyl substitu ents attached to aromatic rings. The oxidation products were separated into dichloromethane-soluble monocarboxylic acids, which were subsequently redu ced to monodeuterated hydrocarbons for characterisation using gas chromatog raphy-mass spectrometry (GC-MS), and water-soluble dicarboxylic acids. n-Al kanes, methylalkanes, alkylalkanes, alkylcyclohexanes, methylalkylcyclohexa nes, isoprenoids and bicyclic compounds were identified in the monodeuterat ed hydrocarbon samples derived from all three aromatic fractions. Most of t hese compounds were the same as those observed in the saturate fractions of unbiodegraded crude oils, except for the deuterium atom. Also, in the samp les from the diaromatic and triaromatic fractions, numerous aromatic compou nds were identified. The main components of the dicarboxylic acid fractions were alpha,omega-dicarboxylic acids and alkylcyclopentane- and alkylcycloh exane-dicarboxylic acids. The oxidation products represent the alkyl moieti es that were attached to aromatic rings in the initial crude oil aromatic f ractions. (C) 1999 Elsevier Science Ltd. All rights reserved.