title: Effect of different lipid extraction methods on delta13C of lipid and lipid-free fractions of fish and different fish feeds.
abstract: For many ecological applications of stable carbon isotope techniques, it is necessary to separate the lipid and lipid-free fractions. The effect of different lipid extraction methods on the isotope signature of the remaining lipid-free matter as well as the lipid fraction was tested. A hot extraction form of the Soxhlet method using petrol-ether was compared with two liquid-liquid extraction methods for lipid determination described by Bligh and Dyer and Smedes. Solid samples of fish and different natural food items were subjected to extraction and the carbon isotope ratios in lipid and lipid-free matter determined by IRMS. All methods were suitable for lipid extraction from all samples analysed here and did not cause biologically relevant differences (> 1%) in carbon isotopic ratios, except the Bligh and Dyer extraction method using chloroform which caused systematic errors for delta13C when applied to diatoms.
authors.affiliation: Department of Aquaculture Systems and Animal Nutrition in the Tropics and Subtropics, Hohenheim University 480b, Fruwirthstr. 12, 70599 Stuttgart, Germany. inst480@uni-hohenheim.de
authors.forename: Ch
authors.initials: Ch
authors.lastname: Schlechtriem
authors.forename: U
authors.initials: U
authors.lastname: Focken
authors.forename: K
authors.initials: K
authors.lastname: Becker
mesh_terms: D000821:Animal Feed; D000818:Animals; D002247:Carbon Isotopes / Q000032:analysis / Q000302:isolation & purification; D002623:Chemistry Techniques, Analytical / Q000379:methods; D002725:Chloroform / Q000737:chemistry; D005399:Fishes; D008055:Lipids / Q000302:isolation & purification; D012997:Solvents / Q000737:chemistry
chemical_list: D002247:Carbon Isotopes; D008055:Lipids; D012997:Solvents; D002725:Chloroform