ASE extraction method for simultaneous carbon and nitrogen stable isotope analysis in soft tissues of aquatic organisms

摘要

Since lipids are depleted in ~(13)C relative to proteins and carbohydrates, variations in lipid composition among species and within individuals significantly influence δ~(13)C and may result in misleading ecological interpretations. Whereas lipid extraction before 1RMS analysis constitutes a way of stable isotope result lipid-normalisation, such a procedure was given up because of the un-controlled effects of the methods used (i.e., "Bligh & Dyer", Soxhlet, etc.) on δ~(15)N. The aim of this work was to develop a simple, rapid and efficient lipid extraction method allowing for simultaneous C and N stable isotope analysis in the biological soft tissues of aquatic organisms. The goal was to be free from the lipid influence on δ~(13)C values without interfering with δ~(15)N values. For that purpose, the modern automated pressurized liquid extraction technique ASE (accelerated solvent extraction) was selected. Eel muscles representative of a broad range of fat contents were extracted via ASE by using different semi-polar solvents (100% dichloromethane and 80% n-hexane/20% acetone) and by operating at different temperature (ambient temperature and 100°C) and pressure (750 and 1900 psi) conditions. The results were discussed in terms of lipid extraction efficiency as well as δ~(13)C and δ~(15)N variability.