June 12, 2022

Solvent extraction method

Extraction is a common technique used in organic chemistry to isolate a target compound. It is the first step to separate the desired natural products from the raw materials. In the extraction process, a solute is transferred from one phase to another to separate it from unreacted starting materials or impurities.

Extraction methods include solvent extraction, distillation method, pressing and sublimation according to the extraction principle.

Solvent extraction: The goal is to use a liquid (solvent) to dissolve (solvate) a target molecule or group of compounds (solute) and to wash them out of the solid plant material. The solvent is then separated from the solute in order to concentrate the solute. This separation is usually achieved by evaporating (distilling) the solvent, which concentrates the solute.

Solvent extraction is a method where chemical compounds are isolated based on their solubilities. Solvent extraction is the most widely used method. The main purpose of solvent extraction is to isolate hazardous materials from the sediments and sludge or separate the useful components from debris. The extraction of natural products progresses through the following stages:
1. The solvent penetrates into the solid matrix;
2. The solute dissolves in the solvents;
3. The solute is diffused out of the solid matrix;
4. The extracted solutes are collected.

The organic solvent selected should be such that:
*The given solid must be much more soluble in the organic solvent than in water.
*The extracting solvent must be immiscible with the solution to be extracted. Water or a water-based solution is usually one of the pair. The other solvent is an organic solvent. The extracting solvent should be sufficiently volatile so that it can be removed easily from the extracted material by distillation.

Volatile solvents such as hexane, benzene, ether, ethyl acetate, and dichloromethane are usually used for the extraction of semi-volatile compounds from water. Hexane is suitable for extraction of non-polar compounds such as aliphatic hydrocarbons, benzene is suitable for aromatic compounds, and ether and ethyl acetate are suitable for relatively polar compounds containing oxygen.

Method
The aqueous solution of the given solute is taken in a separating funnel. It is mixed with the desired organic solvent.

The funnel is closed, and its contents are shaken vigorously. It is then allowed to remain undisturbed for some time. Once the two phases settle back into two layers (in the funnel, the solvent forms the upper layer while the water forms the lower layer) they are separated by opening the stopcock at the bottom of the separatory funnel and allowing one layer to flow out. The liquid that had the solute removed is called the raffinate, while the liquid that gained the solute is called the extract. On evaporating the organic solvent, the solute can be recovered.

Solvent extraction has thousands of applications. It is used in many industries including the petrochemical, pharmaceutical, food, and beverage industries. It's also a common method used to separate and purify elements, proving this process a helpful way to recovery different chemical components.
Solvent extraction method

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