Elephant Head Lipid Extractions

Resultant GC-MS data from Bligh and Dyer extractions of surface soils from Elephant Head, Antarctica.
Given the a very low amount of fatty acids detected in Elephants Head mineral soils, a large lipid extraction uising a modified Bligh and Dyer extraction was applied to the remaining sample material to extract and purify fatty acids from the samples.The protocol was performed on soil samples from two Elephant Head (EH) sites. Total lipid extracts (TLE) were analyzed by GC-MS. Sample run length was 98 minutes. From the Site 1 193.853 grams and from the Lip 2 site 161.774 grams of soil sample were used. Sand blanks contained slight laboratory procedure contamination. Overall, there were 29 peaks identified in the sand blank chromatogram. The area under peaks was analyzed using Agilent MassHunter software, compounds were identified by NIST library search of mass spectra from peaks.
EH Site 1 contained 158 total number of peaks. Peaks were grouped in 6 categories: unique peaks, emulsifier compounds, plasticizer compounds, laboratory contamination, siloxane compounds and peaks that were too low in the mass spectrum signal to successfully identify. Majority of peaks by their count number in the categories were unique peaks (51 %). 30 % came from emulsifier compounds, 1% of plasticizer compounds – indicative of sample contamination. 7 % were peaks from laboratory contamination, 3 % from siloxanes. When comparing groups by peak abundance the most prominent group was emulsifiers (56 %). Unique peaks only were 26 % of the total peak abundance. In the unique peaks there was C16 fatty acid compounds identified, as well shorter chain hydrocarbons, alcohols and ketones. These results suggest contamination in the EH Site 1 sample, that was not present in the sand blank sample. The contamination was probably introduced during sample collection. There is some bacterial signal, however, it is difficult to confidently attribute it to native bacterial signal in the sample site.
EH Lip 2 sample had lower signal then EH Site 1. In the chromatogram there were 69 total number of peaks. Peaks were grouped in 5 categories: unique peaks, emulsifier compounds, plasticizer compounds, laboratory contamination and peaks that were attributed to 9-Hexadecenoic acid, 9-octadecenyl ester, (Z,Z)- as their first match by NIST library. The most abundant groups by number of peaks were 9-Hexadecenoic acid, 9-octadecenyl ester, (Z,Z)- (32 %) and emulsifier compounds and (32 %), then plasticizers (19 %). Unique peaks only covered 13 % of the TLE chromatogram. Lab contamination was 4 %. When plotted by peak abundance per group plasticizer was the most prominent (51 %). Overall, contamination dominated the signal with unique peaks being only 7 %.
Both samples were contaminated. The unique peaks should be used with caution to analyze the biosignatures of the soils as they could have been introduced together with contamination source.