A new method for identifying the origins of simple and complex hopanoids in sedimentary materials using stable isotope labelling with 13CH4 and compound specific stable isotope analyses

Forest soils were taken and incubated with 13C-labelled methane. The lipids from these soils were isolated using a Bligh Dyer extraction and fractionated. Simple hopanoids were present in the neutral fraction, while periodic acid/sodium borohydride treatment of the total lipid extract released primary alcohols from polyfunctionalised bacteriohopane derivatives. All hopanoids were analysed by GC, GC/MS and GC/C/IRMS. Specific hopanoids, namely: diploptene, 17β(H), 21β(H)-homohopanol and 17β(H), 21β(H)-bishomohopanol produced by methane oxidising bacteria were significantly enriched in 13C whilst others showed no enrichment.