GC-MS-MS analysis of bacterial fatty acids in heavily creosote-contaminated soil samples

Phospholipid fatty acid profiles of soil samples enable rapid and reproducible measurement and characterization of the dominant soil microbial communities. When extensive polycyclic aromatic hydrocarbon (PAH) pollution is present in the soil it is very difficult, or even impossible, to distinguish specific fatty acids in GC-MS chromatograms in full-scan mode, because of the PAHs which, because of their lipophilic character, are co-extracted with the lipids. Selected ions in the samples were scanned in MS-MS mode to eliminate the aromatic hydrocarbon signals and obtain clear chromatograms of the fatty acids. By using this technique it was possible to clearly distinguish at least eleven fatty acids in heavily creosote-contaminated soil samples (PAH concentration approximately 15 g kg(-1) dry weight of soil).