Principle of Soxhlet extraction

Soxhlet extraction, also known as continuous extraction, is the most commonly used liquid-solid extraction method and is mainly suitable for the extraction and separation of solid samples. It can analyze lipids or pesticides in food and soil materials and others.

The crude fat content was determined by Soxhlet extraction. Fat is widely found in the seeds and fruits of many plants. Determination of fat content can be used as an indicator to infer its quality. At present, extraction methods have been widely used at home and abroad. The Soxhlet extractor method is a well-recognized classical method and is the preferred standard method for grain and oil analysis in China. This method takes a comparatively short time and is usually extracted in the laboratory using a fat extractor (Soxhlet extractor).

Principle of soxhlet extraction

By using the solvent reflux and siphon principle, the solid matter can be extracted with a pure solvent each time, so the extraction efficiency is high. Prior to extraction, the solid material should be ground to a fine powder to increase the area of the immersion liquid. The solid material is then placed in a filter holder and placed in the extraction chamber. When the solvent is heated to boil, the vapor rises through the air tube and condenses into a liquid, which drops into the extractor. When the liquid level exceeds the highest point of the siphon, siphoning occurs and the solution is returned to the flask so that a portion of the substance dissolved in the solvent can be extracted. Thus, solubles in the solids were concentrated into the flask using solvent reflux and siphoning.

Since the extract of the organic solvent contains more or less fat, such as free fatty acids, sterols, phospholipids, waxes and pigments, the result of the Soxhlet extraction method can only be crude fat.

Compared to traditional solvent extraction methods, Soxhlet extraction saves time and solvent and improves extraction efficiency, but is not suitable for the extraction of thermally unstable components.

The separation effect and enrichment factor are related to the nature of the sample, the extraction temperature, the extraction time, the nature and amount of the solvent. Usually, the substance to be tested is enriched with organic solvent as much as possible while reducing the amount of impurities extracted.