Application Note Soxhlet Extraction

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The Soxtherm Family

Soxtherms Controlled by Soxtherm Manager Software

Traditional Soxhlet System EV6All/16

A Soxhlet extractor is a piece of laboratory apparatus invented in 1879 by Franz von Soxhlet. It was originally designed for the extraction of a lipid (fat) from a solid material. However, a Soxhlet extractor is not limited to the extraction of lipids. Typically, a Soxhlet extraction is only required where the desired compound has only a limited solubility in a solvent, and the impurity is insoluble in that solvent. If the desired compound has a high solubility in a solvent then a simple filtration can be used to separate the compound from the insoluble substance.

Normally a solid material containing some of the desired compound is placed inside a "thimble" made from thick filter paper, which is loaded into the main chamber of the Soxhlet extractor. The Soxhlet extractor is placed onto a flask containing the extraction solvent. The Soxhlet is then equipped with a condenser.

The solvent is heated on a traditional hotplate to reflux. The solvent vapour travels up a distillation arm, and floods into the chamber housing the thimble of solid. The condenser ensures that any solvent vapour cools and drips back down into the chamber housing the solid material.

The chamber containing the solid material slowly fills with solvent. Some of the desired compound will then dissolve in the solvent. When the Soxhlet chamber is almost full, the chamber is automatically emptied by a siphon side arm, with the solvent running back down to the distillation flask. This cycle may be allowed to repeat many times, over hours or days.

During each cycle, a portion of the non-volatile compound dissolves in the solvent. After many cycles the desired compound is concentrated in the distillation flask. The advantage of this system is that instead of many portions of solvent being passed through the sample, just one batch of solvent is recycled.

After extraction the solvent is removed, typically by means of an evaporator, yielding the extracted compound. The non-soluble portion of the extracted solid remains in the thimble, and is usually discarded.

Gerhardt Soxtherm rapid Soxhlet extraction works on a similar principle with a few exceptions and enhancements.

The Soxtherm system does a hot solvent extraction. By immersing the sample in hot solvent the extractable materials are solublised much quicker than in a cold extraction. The solvent is re-circulated to rinse the extractable material into the bottom of the beaker. Finally the solvent is removed by evaporation automatically and recovered for safe disposal or reuse.

The Soxtherm has proved to be a fast, efficient and safe method of Soxhlet extraction for many hundreds of laboratories all over the World.

The latest development in the Soxtherm is the ability to control multiple units from a PC using Soxtherm Manager.

Gerhardt supply both traditional and automated extraction systems, which can be viewed on our product pages by clicking the links.

For a list of available methods or if you would like more information on Soxhlet extraction of your sample please click on the link below.

For more information on Gerhardt Traditional Soxhlet Equipment - click here.

For more information on Gerhardt SOXTHERM Rapid Soxhlet Extraction unit - click here.