What is the principle of organic salting out?

The so-called "salting-out" refers to the addition of inorganic salts such as sodium chloride to the solution of organic macromolecules or some organic polymers.

The process of precipitating organic matter by using the principle of similarity dissolution. In the preparation of ethyl acetate.

Saturated sodium carbonate is used.

Solution reception, more conducive to the precipitation of ethyl acetate, add sodium chloride when making soap, soap is easier to precipitate, add ammonium sulfate in protein solution, so that protein precipitation, all use the principle of salting out.

1.Salting-out: Generally refers to the process of adding inorganic salts to the solution to reduce the solubility of a substance and precipitate.

For example, the process of condensing protein by enriching (NH4)2SO4; In the esterification reaction of acetic acid, saturated sodium carbonate solution is added to reduce the solubility of ethyl acetate and make its stratification phenomenon more obvious.

2.After adding some inorganic salt solutions to some protein solutions, the proteins can be coagulated and precipitated from the solution, which is called salting-out.

3.Put animal fat or vegetable oil with sodium hydroxide.

It is stirred and heated in a saponification pot in a certain proportion, and the high-grade fatty acid sodium, glycerol and water formed after the reaction form a mixture. Add salt particles to the pot, stir and let stand to separate the sodium of advanced fatty acids from glycerin and water, and float on the liquid surface. (This reaction is used to make soap).

The solubility of a protein in an aqueous solution is determined by the degree to which the hydrophilic groups surrounding the protein form a hydration membrane with water, as well as the case in which the protein molecule is charged. When a neutral salt is added to the protein solution, the affinity of the neutral salt for water molecules is greater than that of the protein, so the hydration film around the protein molecules weakens or even disappears. At the same time, after the neutral salt is added to the protein solution, due to the change of ionic strength, a large amount of protein surface charge is neutralized, which leads to the reduction of protein solubility and the aggregation and precipitation of protein molecules.

There is a layer of water film on the surface of the protein to separate the protein molecules from each other, so as to avoid the condensation and precipitation between the molecules. <>

Salting-outIt refers to the phenomenon that neutral salts are added to the aqueous solution of proteins, and the proteins are precipitated with the increase of salt concentration. Neutral salt isStrong electrolytes, the solubility is large, and in the protein solution, on the one hand, it competes with the proteinWater molecules, destroying the water film on the surface of protein colloidal particles; On the other hand, a large amount of the charge on the protein particles is neutralized, so that the protein particles in the water accumulate and precipitate.

Principle of salting out crystallization:

Salting out crystallization refers to the addition of a certain electrolyte salting out agent in the salt solution system, the added salting out agent, the hydration of its ions is stronger than other salts in the original solution, it reduces the number of free water molecules in the solution, so as to increase the effective concentration of the substances to be crystallized in the solution, so that the substances to be crystallized are crystallized and precipitated in the solution, which is salting out crystallization.

Studies have shown that water has a positive effect on anions and cations.

All have strong solvation effect.

But for cations than anions.

There is a greater solvation effect. Therefore, the salting out agent is mainly manifested in the cationic solvation of the salting out agent. The stronger the salting out agent is combined with water, the stronger the salting out effect. Since the hydration number is related to the size of the ion, that is, the smaller the ion, the greater the hydration number, and the stronger the salting out effect.

The smaller the cation radius and the more charge the salting out agent, the greater the influence on the hydration layer of the salted out ions, the easier it is to dehydrate the salted out ions, and the stronger the salting out effect. Therefore, most of the salting out agents commonly used in chemical production are salts formed by cations with large ionic potential, such as Li+, Al3+, Fe3+, Mg2+, and Sn2+.

The principle of salting out method is to add ammonium sulfate, sodium sulfide or sodium chloride to the protein solution, so that the surface charge of the protein is neutralized and the hydration membrane is destroyed, resulting in the removal of the stability factors of the protein in the aqueous solution and precipitation.

After the neutral salt is added to the protein crying solution, the affinity between the neutral salt and the water molecule is greater than that of the protein, resulting in the weakening or even disappearance of the hydration layer around the protein molecule. At the same time, after the neutral salt is added to the protein solution, due to the change of ionic strength, the charge on the surface of the protein is neutralized in large quantities, which leads to the reduction of protein solubility, and the aggregation and precipitation of protein molecules.

Application of salting-out method

The salting out of colloids is the process of adding salt to reduce the solubility of colloids and form precipitation, which is a kind of aggregation and precipitation phenomenon of colloids, such as adding some concentrated inorganic salts [such as (NH4)2SO4 or Na2SO4] solution to the protein solution, which can make the protein coagulate and precipitate from the solution, which is called salting-out.

In this way, the precipitated egg Zhengwan cryptowhite matter can still be dissolved in water without affecting the properties of the original protein. Therefore, salting out is a reversible process. Taking advantage of this property, proteins can be separated and purified by multiple salting out methods.

The solubility of a protein in an aqueous solution depends on the number of water molecules surrounding the ions on the surface of the protein molecule.

That is, it is mainly determined by the degree to which the hydrophilic groups around the protein molecule form a hydration film with water and the case that the protein molecule is charged. After the neutral salt is added to the protein solution, the affinity between the neutral salt and the water molecule is very fast to the protein, resulting in the weakening or even disappearance of the hydration layer around the protein molecule.

The above content reference:Encyclopedia - Salting-out method

The process of adding inorganic salts to the solution to reduce the solubility of a substance and precipitate it, such as the process of condensing proteins by adding (NH4)2SO4, and adding saturated sodium carbonate solution in the esterification reaction of acetic acid to reduce the solubility of ethyl acetate and make its stratification more obvious.

After sodium chloride is dissolved and ionized in water, the concentration of chloride ions and sodium ions in water is greater than that at the water cyclohexene interface, resulting in a higher water cyclohexene interface energy and a system that tends to decrease the interface. It is not conducive to the dispersion of cyclohexene in water, nor is it conducive to the dispersion of water in cyclohexene.

1. Destruction of the hydration layer.

In a high concentration of neutral salt solution, because the salt ions are more hydrophilic than proteins, they compete with protein colloids to bind to water, destroying the hydration layer of proteins.

In a high-concentration neutral salt solution, because the protein and salt ions are attractive to the water molecules in the solution, the phenomenon of hydration is produced, but there is a competition between them, when a large number of neutral salts are added, the ions produced by salt dissociation compete for most of the free water in the solution, thereby destroying the hydration of the protein, causing the protein solubility to decrease, so it is precipitated from the solution.

2. Destroyed the charge.

Since salt is a strong electrolyte with strong dissociation effect, the dissociation of salt can inhibit the dissociation of weak electrolytes of proteins, so that the charge of proteins is reduced, and it is easier to aggregate and precipitate.

Salting-out: Generally, Sochangyou refers to the process of adding inorganic salts to the solution to reduce the solubility of a substance and precipitate. Such as:

The process by which the protein is coagulated by the enrichment of (NH4)2SO4; In the esterification reaction of acetic acid, saturated sodium carbonate solution is added to reduce the solubility of ethyl acetate and make its stratification phenomenon more obvious.

2.After adding some inorganic salt solutions to some protein solutions, the protein can be rapidly agglomerated and precipitated from the solution, which is called salting-out.

3.Animal fat or vegetable oil and sodium hydroxide are stirred and heated in a saponification pot in a certain proportion, and the high-grade fatty acid sodium, glycerol and water formed after the reaction form a mixture. Add salt granules to the pot, stir and let stand so that the sodium of high-grade fatty acids, glycerin and water are separated and float on the liquid surface.

(This reaction is used to make soap).