A simple and rapid solvent extraction method for determining total lipids in fish tissue.

Solvent systems that have been developed for lipid extraction include chloroform-methanol, n-hexane-isopropyl alcohol, and methylene chloride-methanol. The extraction methods are labor intensive, lack precision, or require a large volume of solvent. Correct computation of lipid content calls for full recovery of solvent after extraction, but recovery always is incomplete because of unaccounted solvent residue that remains in jar, filter paper, and homogenized tissue. A rapid and simple extraction method coupled with correct computation was developed for determining total lipids in fish tissue. The method uses chloroform-methanol and an Eberbach blending jar. Variables examined were chloroform-methanol ratio, solvent-to-sample ratio, and phase separation time. Precision was within 0.5%. Conventional computation of lipid content depends on the volume of chloroform measured after filtration. This volume does not include unaccounted solvent residue. Thus, a time-consuming second extraction is required for complete recovery. The mass balance of each extraction and filtration step confirmed that the correct volume of chloroform (measured plus unaccounted) was close to the theoretical volume. The procedure eliminates problems associated with laborious filtration and variation in chloroform volume readings and does not require an exact reading of chloroform volume. Instead it allows use of a theoretical volume, which depends on solvent volume and ratio used.