A Quantitative Lipid Extraction Method for Residue Analysis of Fish Involving Nonhalogenated Solvents

Abstract

Numerous intercalibration exercises have indicated that the in Sweden frequently used, so called Jensen extraction method for total lipids and lipophilic pollutants gave satisfactory yields when applied to fatty aquatic organisms. However, a comparison with the classical Bligh and Dyer method and the forerunner, the Folch methods, revealed that in the case of very lean fish (fat content below 1%, e.g., cod), the lipid yields were about 25% too low for the Jensen method; consequently, residue levels quoted on a lipid weight basis were correspondingly too high. To rectify the unacceptably low fat recovery from lean marine organisms, the Jensen extraction method has been modified to give recoveries not significantly different from the Folch and Bligh and Dyer methods. In the modified version, acetone is replaced by 2-propanol and part of the hexane is replaced by diethyl ether. Comparison between the modified Jensen method and the Folch method for cod muscle gave the same recovery of total lipids but slightly lower than that obtained with the Bligh-Dyer method. A possible explanation for this small difference is discussed. It is anticipated that the reported increased yield for cod is due to the superior solubility of phospholipids in 2-propanol as compared to acetone. The possible use of correction factors for previously reported contaminant residual levels of lean and medium fat fish calculated on lipid basis in the future is suggested.

Determination of lipid content in fish samples from bioaccumulation studies: contributions to the revision of guideline OECD 305

“…Both techniques are described in detail in Additional file 2. An alternative method for the quantitative extraction of lipids from fish using non-halogenated solvents was described by Jensen et al [6]. Lipid recoveries comparable to the Bligh and Dyer method were obtained for cod muscle, showing the high potential of this method.…”

“…Investigations in the aquatic environment have revealed a significant positive correlation between the accumulation of a chemical and the lipid content of organisms, and residue levels thus differ between individuals, species, and size groups depending on their lipid contents [2][3][4]. Therefore, variations in these data can be reduced when BCF values are normalized by lipid content [5,6]. Furthermore, this facilitates the extrapolation between species and sites.…”

“…The results obtained with different extraction methods may differ quite considerably [6,8,9,[12][13][14][15][16][17][18], leading to over-or underestimations when normalizing BCF values to lipid contents. Therefore, the selection of appropriate extraction techniques using mixed systems of nonpolar and polar solvents is required to ensure the complete extraction of total lipids from fish/tissue samples.…”

Brominated Flame Retardants (BFR) in the Nordic Environment

“…The sample was fortified with an internal standard, acidified, homogenized and extracted according to Jensen et al (2003). The extract was dried and stored in a freezer (-18°C) until derivatisation with diazomethane and clean-up (se below).…”

Neutral and phenolic brominated organic compounds of natural and anthropogenic origin in northeast Atlantic Greenland shark (Somniosus microcephalus)

“…At SU, 10 g of homogenized muscle and liver tissue was extracted according to Jensen et al [27], except that cyclohexane was used instead of n-hexane. Brominated diphenyl ether-71 (2.5 ng) and 4 0 -OH-BDE121 (0.5 ng) was added to 1 g of fat as surrogate standards for neutral and phenolic compounds, respectively.…”