Synthesis of Anaerobic Degradation Biomarkers Alkyl-, Aryl- and Cycloalkylsuccinic Acids and Their Mass Spectral Characteristics

Abstract

Anaerobic biodegradation of petroleum hydrocarbons has been reported to proceed predominantly via fumarate addition to yield substituted succinate metabolites. These metabolites, commonly regarded as signature biomarkers, are specific indicators of anaerobic hydrocarbon degradation by microbial activity. To the best of our knowledge, mass spectrometry information for 2-(1-methylalkyl) succinic acids, 2-arylsuccinic acids, 2-cycloalkylsuccinic acids and/or their derivatives is still incomplete, especially for the analysis of environmental samples. Here, a novel approach is proposed for the successful synthesis of five hydrocarbon-derived succinic acids. The characteristic fragments of 2-(1-methylalkyl)succinic acid diesters were investigated by four derivatization processes (methyl, ethyl, n-butyl and trimethylsilyl esterification), some of which are not available in official libraries. Under electron ionization mass spectrometry conditions, informative fragments of various molecular masses have been obtained. Results confirmed characteristic differences among the derivatization processes of the chemically synthesized compounds. In the case of 2-(cyclo)alkylsuccinate esters, four intermediate fragments were observed at m/z 114 + 14 n, 118 + 28 n, [M – (17 + 14 n)]+ and [M – (59 + 14 n)]+ ( n = 1, 2 and 4 for methyl, ethyl and n-butyl ester). However, for silylation the abundant fragment ions are at m/z 262, 217, 172, 147, 73 and [M − 15]+. These data provide information for the identification of hydrocarbon-derived succinic acids as anaerobic biodegradation intermediates in hydrocarbons-rich environments.