Dear all, We are pleased to share our recent publication on lipid extraction methods for stable isotope analysis of beaked whale tissue.
Smith, KJ, Trueman, CN, France, CAM, Peterson, MJ. Evaluation of two lipid removal methods for stable carbon and nitrogen isotope analysis in whale tissue. *Rapid Commun Mass Spectrom*. 2020. https://0-doi-org.lib.utep.edu/10.1002/rcm.8851 The presence of lipids in animal tissues can influence the interpretation of stable isotope data, particularly in lipid‐rich tissues such as the skin and muscle of marine mammals. The traditionally employed chloroform:methanol delipidation protocol has the potential to alter δ15N values in proteinaceous tissues. Our objective was to determine whether cyclohexane is an alternative extraction method, effectively removing lipids without altering δ15N values. Kidney, liver, muscle, and skin samples were collected from beach‐cast Sowerby's beaked whales (*Mesoplodon bidens *). Control subsamples were processed without delipidation extraction, and duplicate subsamples were extracted with either chloroform:methanol or cyclohexane. δ13C, δ15N, and C:N values were determined by continuous‐flow elemental analysis isotope ratio mass spectrometry. Paired Wilcoxon tests were used to evaluate the change in isotope ratios after extraction, and unpaired Wilcoxon tests were used to evaluate difference in isotope ratios between extractions. Cyclohexane is an effective delipidation technique for tissues with low and moderate lipid content. Chemical delipidation influenced δ15N values; extracted samples generally showed an increase in δ15N values which varied from 0.0‰ to 1.7‰. Chloroform:methanol extraction resulted in alterations to δ15N values greater than the analytical precision for all analyzed tissues. Changes to δ 15N values after cyclohexane extraction were at or near the analytical precision in liver and muscle but greater than the analytical precision for kidney and skin. We recommend processing duplicate subsamples for stable isotope analysis, one with and one without extraction in order to obtain accurate values for each isotope ratio. Prolonged chemical extractions are not necessary to effectively remove lipids. When samples are limited, we suggest using cyclohexane for tissues with low or moderate lipid content, and chloroform:methanol for lipid‐rich tissues. Cheers, Kerri *--Kerri J. Smith, Ph.D.* Postdoctoral Researcher- Laboratory of Ecological and Adaptational Physiology Research Fellow - Smithsonian Institution Website <https://kerrijsmith.wordpress.com/> “The love for all living creatures is the most noble attribute of man.” -Charles Darwin
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