How to perform column separation and purification of compounds, the operation process, and the exper

Experimental Instruments and Drugs:

Chromatography column (if you buy a sand core at the bottom, then you don't have to do it yourself, if not, you need to buy absorbent cotton to rub it into a spindle-shaped plug at the lower end of the chromatography column to avoid the stationary phase flowing out with the eluent), expansion tank (a grinding mouth of the wide-mouth small glass bottle, the formal name is not very clear, it seems to be called this), silicone plate (if you buy it without cutting, you have to buy a glass knife to cut it yourself), ultraviolet lamp (to see the color of the running board, If your product is not good for color development, you should first use a solution of concentrated sulfuric acid to develop the color, this is your own), rotary evaporator and its attached glass instruments, glass capillaries, hair dryers (for blowing boards, don't just need to wait for a while), other commonly used glass instruments in laboratories, etc.

Appropriate polarity of mobile phase (also known as eluent, commonly used methanol, dichloromethane, ethyl acetate, petroleum ether and other systems, you need to adjust the polarity according to the nature of the product), stationary phase (also the core of column chromatography, generally buy silica gel or anhydrous alumina for column chromatography).

Experimental operation: Generally, you need to do the solubility test and polarity test of your impure product (let's say it is a mixture of 1 and 2, 1 is our target product, and we want to separate 1) (I have done dichloromethane methanol system for example). Dissolve the mixture in methylene chloride first, and then check the running board.

If you feel that you can't run away at 1,2 points (i.e., the separation is not obvious on the silicone board), gradually increase the polarity with dichloromethane:methanol 50:1 to 10:

1 (volume ratio) of the mixture is measured gradually, with two points more clearly divided as the boundary, note this ratio, and configure more. (Assuming that the situation of the running board is 1 in the back and 2 in the front, that is, 2 polarity is large).

Then the column is loaded (be careful not to let the silica gel or alumina leak from the bottom, and if necessary, add a layer of absorbent cotton), then load the sample, rinse it with the mobile phase and monitor the plate without stopping. 2 has a large polarity, so 2 will come out first, collect him and steam him for later use. 2. After rinsing, if your polarity is well adjusted, 1 will not be mixed together, there will be a blank layer in the middle, and 1 will also come out if you continue, collect it and then concentrate it by spinning and steaming, you can get 1 pure product.

Methods of separation and purification

1. System solvent separation method.

The most commonly used method is to concentrate the ethanol or methanol extract of traditional Chinese medicine properly, mix it evenly with a certain support (such as diatomaceous earth, silica gel, etc.), and after drying, use solvents with different polarities, and extract them from small to large. Then choose a method to isolate the reputation. It is also possible to directly extract the coarse powder of medicinal materials with solvents of different polarities to obtain each part.

2. Two-phase solvent extraction.

The extraction method is a method of separating the components of the mixture by using different partition coefficients in immiscible solvents. The isolate can be dissolved in water and extracted with an organic solvent that is immiscible with water, or the isolate can be dissolved in an organic solvent immiscible with water and extracted with an appropriate pH of water to achieve the purpose of separation.

3. Selective redox method.

Use appropriate oxidants or reducing agents to oxidize or reduce some components in the mixture, and further achieve the purpose of separation and purification.

4. Absorption and adsorption method.

Absorb certain components of the mixture with suitable reagents, such as caustic soda to absorb carbon dioxide from the gas mixture. Or use a number of appropriate substances to adsorb some components in the mixture, such as adsorbing some gases with activated carbon, so as to achieve the purpose of separation and purification.

5. Liquid solvent extraction method in the liquid Wang Bi section.

Select a suitable solvent to dissolve and absorb some components in the mixture, so as to achieve the purpose of separation and purification.

6. Distillation.

The condensation temperature of the vapor of the mixed solution is controlled, so that the components with different boiling points are condensed and precipitated step by step, so as to achieve the purpose of separation and purification.

For non-polar components, alumina or silica gel adsorption chromatography is often considered; If the polarity is large, partition chromatography or weak adsorbent adsorption chromatography is used; Ion exchange chromatography can be used for acidic, basic, and amphoteric components, and sometimes adsorption chromatography and partition chromatography can also be used.

Summary. The process flow and method of separating mixtures by column chromatography are discussed: column chromatography, also known as chromatography. It is a distribution method based on the mechanism of distribution equilibrium. Column chromatography is mainly divided into adsorption column chromatography and distribution column chromatography.

The process flow and method of separating mixtures by column chromatography are discussed: column chromatography, also known as chromatography. It is a distribution method based on the mechanism of distribution equilibrium. Column chromatography is mainly divided into two types: adsorption column Bixing chromatography and distribution He Huiling column chromatography.

1.Adsorption column chromatography principleUnder certain conditions, the silica gel and the separated substance are destroyed before the shed, and this effect is mainly physical and chemical. The physical action comes from the van der Waals force between the surface of the silica gel and the solute molecules.

The chemical action is mainly the hydrogen bonding between the silica hydroxyl group on the surface of the silica gel and the substance to be separated. The chromatography tube is a rigid glass tube with uniform inner diameter and a necked lower end, the lower end is plugged with cotton or glass fiber, and the tube is filled with adsorbent. The particles of Huibei adsorbent should be kept as uniform in size as possible to ensure good separation.

Unless otherwise specified, particles with a diameter are usually used. The size of the column, the variety and amount of sorbent, and the flow rate during elution are all specified under each variety. In adsorbent column chromatography, the sorbent is the stationary phase and the eluent is the mobile phase, which is equivalent to the agent in thin layer chromatography.

The basic principle of the adsorbent is the same as that of adsorption thin layer chromatography, which is also based on the difference in adsorption strength between each component and the adsorbent, and is completed by repeatedly carrying out adsorption, desorption, readsorption, and redesorption on the column chromatography. The difference is that during column chromatography, the mixed sample is typically added to the top of the column, and the mobile phase flows through the column from the top of the column and out of the column continuously. Because the components in the mix have different adsorption to the adsorbent, the components move with the mobile phase at different velocities in the column, resulting in sequential elution of the components from the column.

If the outgoing eluent is received in steps, the mixture can be separated.

2.The principle and method of distribution column chromatography are basically the same as those of adsorption column chromatography. Before loading the column, the carrier and stationary solution were mixed, and then moved into the column in stages and pressed with a flat glass rod; The test sample can be dissolved in front of the stationary solution, mixed with a small amount of carrier, and added to the upper end of the prefabricated chromatographic column.

The eluent should be saturated with a fixative solution to avoid the change of the two-phase distribution of rock and slow during the elution process.

Extraction is a common unit operation in chemical engineering for separating liquid mixtures.

Extraction, also known as solvent extraction or liquid-liquid extraction, also known as extraction, is a unit operation that uses the different solubility of components in a system to separate a mixture in a solvent. That is, it is a method to transfer solute substances from one solvent to another solvent by using the difference in solubility or partition coefficient of two incommiscible orange (or slightly soluble) solvents. It is widely used in chemical, metallurgical, food and other industries, and is commonly used in petroleum refining industry.

In addition, the operation of separating the two immiscible liquids after extraction is called dispensing.

Extraction is one of the methods used in organic chemistry laboratories to purify and purify compounds. By extraction, the desired substance can be extracted from a solid or liquid mixture.

1) Sedimentation separation method.

Features: It is suitable for the coarse separation of aqueous extracts with high solid content, which is simple and easy. However, it takes a long time, the residue precipitates and adsorbs a lot of liquid medicine, and it is not suitable for those who have less solid content in the material liquid, fine and light particles, and the material liquid is easy to spoil and deteriorate.

2) Centrifugal separation.

1.Classification by the size of the separation factorThe larger the separation factor, the stronger the separation capacity of the centrifuge.

2.According to the centrifugation process, the separation process in the centrifuge can be divided into: centrifugal filtration. Centrifugal sedimentation. Centrifugal clarification.

Zhen Gao III) filtration separation method.

In actual operation, filter aids are often added to the feed solution to improve the performance of the filter residue and increase the filtration rate. Depth filtration: suitable for liquids with fine particles and low content.

2.Filtration speed and influencing factors The larger the pressure difference (p) between the two sides of the filter residue layer, the greater the filtration rate. Pressurized or reduced-pressure filtration is often used. However, when the pressure is high to a certain extent, the filter resistance is increased due to the compacting of the filter cake, and the filtration rate is reduced.

At the beginning of filtration, the filtration speed is proportional to the area of the filter (r2).

The filtration rate is proportional to the capillary radius (R) of the filter media or cake.

The filtration rate is inversely proportional to the capillary length ( ).

The filtration rate is inversely proportional to the viscosity of the feed ( ).

3.Filtration methods and equipment (1) The atmospheric pressure filtration method is generally suitable for the filtration of small amounts of liquid medicine.

2) Vacuum filtration method is generally medium to a large amount of liquid medicine filtration.

3) Plate and frame filter press is commonly used for pressure filtration, plate and frame filter press is suitable for liquid with low viscosity and less slag for closed filtration, and alcohol sediment and mixture are mostly used for plate and frame filtration.

4) Membrane filtration method.

Membranes are used to filter media, microporous membrane filtration, ultrafiltration microporous membrane filtration are used to filter out bacteria and fine suspended particles. It is mainly used for fine filtration in production, such as the filtration of water injection and large infusion ants; Sterilization and purification of heat-sensitive drugs.

The characteristics of microporous membrane filtration are: the pore size of the microporous membrane is relatively uniform, the porosity is high, accounting for about 80% of the total volume of the membrane, so the filtration rate is fast; The filter membrane has a thin texture (, the filtration resistance to the material liquid is small, and the adsorption is less; No medium falls off during filtration, and there is no pollution to the liquid medicine; However, it is easy to clog, so the material liquid must be pre-filtered first.

Ultrafiltration refers to the use of thin membranes, smaller pore sizes, and specific structures as filtration media, which penetrate small molecule solutes and intercept macromolecular solutes. Ultrafiltration is a technique for selective filtration in the order of nanometers (nm). The pore size specification of ultrafiltration membrane is generally based on the relative molecular mass cut-off value.

Decanting: Separation of dense and insoluble solids from liquids.

Separation of sand and water.

Filtration: Separation of insoluble solids from liquids.

Purified drinking water.

Dissolution and filtration: Separation of two solids, one soluble in a solvent and the other insoluble in the separation of salts and sand.

Centrifugal separation: Separation of insoluble solids from liquids.

Separation of mud and water.

Crystallization: Separation of dissolved solutes from solution.

Extraction of table salt from seawater.

Dispensing: Separation of two immiscible liquids.

Separation of oil and water.

Extraction: Add appropriate solvent to dissolve and separate a component in the mixture, and extract iodine in aqueous solution with heptane.

Distillation: Separation of solvents and non-volatile solutes from solution.

Pure water is obtained from seawater.

Fractionation: Separation of two liquids that are miscible with large differences in boiling points.

separation of oxygen and nitrogen from liquid air;

Petroleum refining.

Sublimation: Separating two solids, only one of which can be sublimated.

Separation of iodine and sand.

Adsorption: Removal of gaseous or solid impurities from the mixture.

Activated charcoal is used to remove colored impurities from brown sugar.

Chromatography: Separation of solutes in solution.

Separation of different colored substances in black ink.

Separation and purification of mixtures.

1.Physical methods.

1) Filtration: It is a method to separate insoluble solids from solutions by using the difference in solubility of each component of the mixture in the same solvent. Such as the purification of coarse salt.

2) Evaporation concentration: It is a method used to separate solutes dissolved in solvents. Such as the separation of NaCl. in table salt solution

3) Crystallization and recrystallization: It is a method to separate and purify substances by using the different properties of the solubility of each component in a mixture in a certain solvent with different temperature changes. Such as the separation of NaCl and Kno3 mixtures.

Recrystallization is actually a repeated operation of dissolution and crystallization.

4) Distillation and fractionation: It is a method of separating substances by using the properties of several miscible liquids with large differences in their respective boiling points. Such as the separation of various fractions from petroleum, and then the separation of C2H5OH and H2O mixtures.

Aluminum can react with sodium hydroxide solution, and sodium hydroxide can be used to remove the aluminum powder in the iron powder, and then filter to obtain iron; Sulfur dioxide can react with saturated sodium bicarbonate solution to form carbon dioxide gas, which can be separated by the method of gas washing, so the answer is:

fe（al）

co2（so2）

Reagent sodium hydroxide solution.

Saturated sodium bicarbonate solution.

Method: Dissolve and filter the washing gas.