Isomers of the dodecylbenzene in marine sediments from the Todos os Santos Bay, Bahia, Brazil

Abstract

Linear alkylbenzenes(LAB) have been investigated in sur®cial sediments from the Todos os Santos Bay, the largest on the Brazilian coast. The presence of these compounds in the environment has been related to sewage pollution because they are manufactured for the preparation of surfactants used in detergent formulations. They are usually present as an homologous series of compounds with a side chain varying from 10 to 14 carbon atoms attached to a benzene ring. The sediment samples were collected from the intertidal area of 13 stations situated in the bay. The dried samples were solvent extracted, and after clean up and fractionation of the lipid extract by column chromatography the fraction containing the LABs were separated and identi®ed by high resolution gas chromatography and gas chromatography coupled to mass spectrometry. Surprisingly, only the isomers of dodecylbenzene were found. The compounds were present in all stations and the concentrations ranged from 0.063 to 50.2 mg g21 total organic carbon. These values were considered very high compared to those cited in the literature. It is not yet clear if the origin of these compounds in the sediments is related to detergent formulations. However, the results suggest that they possibly originated from a point source and dispersed in the bay probably due to water movements in the area.