Soxhlet Extraction: Principle, Extraction procedure, and Apparatus

Table of Contents

Soxhlet extraction is an advanced extraction technique that involves repeatedly circulating the same solvent through the extractor. In 1879, Franz Ritter von Soxhlet, professor of agricultural chemistry at the Technical University of Munich, developed this extraction technique. This is a very useful technique for preparative goals in which the analyte is concentrated from the matrix as a whole or separated from specific interfering substances.

Principle

The Soxhlet extraction method uses a small amount of solvent and is very cost-effective. The Soxhlet extraction uses the solvent reflux and siphon principle to continuously extract the solid matter by pure solvent, which saves the solvent extraction efficiency and high efficiency. The sold sample is placed on a thimble-shaped filter paper, positioned into the Soxhlet extractor, and the device is assembled.  The solvent is added to the solvent reservoir flask and mounted onto a heating mantle. After heating, the condensed vapors of the solvent come in contact with the sample powder, and the soluble part of the powder gets mixed with the solvent for extraction. When the solvent surface exceeds the maximum height of the siphon, the solvent containing the extract is siphoned back. The flask is repeated, extracting a portion of the material each time so that the solid material is constantly used as a pure solvent and the extracted material is concentrated in the flask.

Soxhlet extraction procedure

The crude substance is placed in a thimble-shaped filter paper which is then kept in a glass cylinder. This cylinder is provided with a siphon tube and an inlet tube. A water condenser is attached to the cylinder at the top. This entire assembly is fitted into the neck of a round bottom flask containing the solvent.

Soxhlet extraction procedure
Soxhlet extraction procedure

The flask is heated in a water bath or sand bath. The solvent vapors reach the cylinder through the inlet tube and conduce on passing upward into the condenser. The condensed solvent comes in contact with the crude organic substance and dissolves it. As soon as the solution reaches the top end of the siphon tube. In this way, a continuous supply of solvent vapors is maintained in the cylinder, and the dissolved organic compound flows back into the flask. Finally, the heating is stopped and the solution in the flask is distilled to recover the solvent, While the organic compound is left behind.

Uses

  1. The soxhlet extraction process is the most useful technique for solid-liquid extraction in many fields like Agriculture, pharmaceuticals, foodstuffs, and also in the environment.
  2. Soxhlet apparatus is allow for continuous treatment of a sample with a solvent over a period of hours or days to extract the compound of interest.
  3. This technique is useful to determine the lipid and fat contents of animal and plant tissue.
  4. This is also used to determine the percent of fat content in a food sample by weight in a sample.

FAQs

What is soxhlet extraction?

Soxhlet extraction is an advanced extraction technique that involves repeatedly circulating the same solvent through the extractor.

What principle is used in the soxhlet apparatus?

The Soxhlet extraction uses the solvent reflux and siphon principle to continuously extract the solid matter by pure solvent, which saves the solvent extraction efficiency and high efficiency. 

Soxhlet extraction

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