The definition of chemical separation, the difference and connection between the two concepts of ana

Chemical separation refers to the fact that the sample is often separated from the interfering substance before it can be measured (or detected).

Commonly used separation methods.

Distillation, sublimation, crystallization, precipitation, solvent extraction.

Ion exchange, chromatographic separation, centrifugal separation, electrodialysis, electrochemical separation methods, salting out.

Chemical separation: The chemical separation of different substances (in the same system).

For example, artemisinin is isolated from Artemisia annua using an extraction process. Dissolve ** from quartzite with thiourea solution. Chromatographic separation of specialty proteins from the stock solution. Wait a minute.

1. Precipitation.

Separation BAI method: chemical reaction or addition that uses the formation of sedimentary deposits.

The precipitated DAO agent destroys the special stability of the colloidal solution so that the sample components are precipitated and deposited, and then the precipitated components are obtained (or discarded) by filtration or centrifugation.

2. Extraction and separation method: the fat-soluble molecules are extracted with organic solvents and then volatilized to remove the solvent.

3. Chromatographic separation method: when the sample flows through the chromatographic column, each component is separated one by one due to different residence times on the column due to physical and chemical reasons.

4. Electrophoretic separation method: It is established according to the phenomenon that the dotted particles move towards the electrode opposite to their electrical properties under the action of the electric field.

5. Centrifugal separation method: It is a method to realize the separation of substances under the action of centrifugal force by using the different sedimentation coefficients of colloidal solutes.

6. Ultrafiltration separation method: The ultrafiltration membrane (a semi-permeable membrane) is loaded into a centrifuge tube, and the passage of the solution is accelerated by centrifugal force.

There are no 11 separation methods, and most of them are branches of separation methods such as extraction, membrane separation, filtration, chromatography, salting-out, etc.

1. Extraction. 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 of transferring solute substances from one solvent to another solvent by using the difference in solubility or partition coefficient of substances in two immiscible (or slightly soluble) solvents.

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.

2. Membrane separation method.

A chemical separation method that uses the semi-permeability of a thin film to separate a mixture of solutions, which separates certain components from a gaseous or liquid mixture.

The membrane used can be micropores with certain specifications, like molecular sieves, allowing small molecules to pass through the pores and large molecules to intercept the flow, so that the mixture can be separated; It can also be a non-porous polymer membrane, where some components in the mixture are first dissolved on the surface of the membrane, then diffuse through the membrane layer, and finally evaporate on the other side, thus achieving the purpose of separation.

3. Filtration. The liquid (or gas) in the suspension (or the hot gas containing solid particles) under the action of the driving force or other external forces penetrates the medium, and the solid particles and other substances are intercepted by the filter medium, so that the solids and other substances are separated from the liquid (or gas).

4. Chromatography. A method for separating and measuring multi-component mixtures by taking advantage of the different physical properties of each component. There are two types: adsorption chromatography and partition chromatography. It is generally used for the analysis of organic compounds, metal ions, amino acids, etc.

Chromatography is a technique that uses different partitioning ratios of substances between the stationary phase and the mobile phase to achieve the purpose of separation.

Chromatography has high resolution for the separation and analysis of complex mixtures of biological macromolecules, such as proteins and nucleic acids.

5. Salting-out. After adding some inorganic salt solutions to some protein solutions, the solubility of the protein can be reduced, so that the protein can be coagulated and precipitated from the solution, which is called salting out, which is a physical change and can be restored.

Adding certain heavy metal salts to some protein solutions can change the properties of the protein and condense, and then precipitate from the solution, this effect is called denaturation, property change, is a chemical reaction, and cannot be recovered.

Protein precipitation is made by using high concentrations of neutral salts; The solubility (s) of the protein is different, and the concentration of salt used for precipitation is different.

1.Crystallization and recrystallization: The solubility of the utilized substances in the solution varies greatly with temperature, such as NaCl, Kno3.

2.Distillation: Large difference in boiling point. In ethanol (water): Add freshly made CAO to absorb most of the water and then distill.

3.Filtration: soluble and insoluble.

4.Sublimation method: SiO2 (I2).

5.Extraction method: For example, Ccl4 is used to extract I2 in water.

6.Dissolution method: Fe powder (A1 powder): dissolved in excess NaOH solution and filtered and separated.

7.Addition method: convert impurities into the desired substance: CO2 (CO): Cuo through heat; CO2 (SO2): by NaHCO3 solution.

8.Absorption method: used to remove gas impurities in the mixed gas, gas impurities must be absorbed by the drug: N2 (O2): The mixed gas absorbs O2 through the copper mesh.

9.Transformation method: it is difficult to separate the two substances directly, and the added drug becomes easy to separate, and then reduced back:

Al(OH)3, Fe(OH)3: Add NaOH solution to dissolve Al(OH)3, filter, remove Fe(OH)3, and then add acid to convert NaALO2 into A1(OH)3.

10.Paper-based chromatography.

11.Heating method: If sodium bicarbonate is mixed with sodium bicarbonate, the heating method is used to decompose sodium bicarbonate into sodium carbonate.

12.Dialysis: suitable for the purification of colloids. If the starch is mixed with sodium chloride, the sodium chloride in the starch colloid can be removed with a semi-permeable membrane.

13.Salting out method: suitable for protein purification.

Separation is the process of using the differences in the physical or chemical properties of each component in a mixture to distribute each component to different spatial regions or to the same spatial region at different times through appropriate devices or methods. Analytical chemistry is the development of methods for analyzing the composition and structure of substances, so that the chemical composition can be qualitatively and quantitatively determined, and the chemical structure can be determined.

Differences: 1. Different purposes.

Chemical analysis is to determine the structure of a substance, and separation is to separate related substances from a substance.

2. The characteristics are different.

Chemical analysis is to determine the content of the components, and separation is to separate the components without determining the content.

3. The methods are different.

Analytical methods such as electrophoresis, chromatography, field-flow fractionation, etc. are often used. Separation: salting-out, extraction and separation methods (including solvent extraction, micelle extraction, and aqueous phase extraction.

The mixture of NaCl and Nabr is an experimental phenomenon in which the exact existence of two substances is obtained by chemical or physical means, and the separation refers to the acquisition of pure NaCl and Nabr, and the premise of separation is to carry out accurate chemical analysis of the substance.

Analysis: Chemical analysis, the process of component qualification, i.e. the process of determining the number of each component. Target.

Separation: Product separation, in this process, is formed into a similar or identical component species of separated parts, that is, in the process of mountain bark from the mixture, to obtain a more amusement and pure compound.

Chemical analysis often involves a rapid separation process.

Extraction. It is separated by physical means.

Requirements: First, the two solvents used must be incompatible.

Second, the solubility of the solute (that is, the substance you want to extract) in the two solvents must be different.

Dispensing. It is also a physical method.

It is to use the incompatibility of the two solutions, and there is a layer when the two solutions are put together.

Then, dispense with a separating funnel.

Fractionation. It is to use the different boiling points of various substances to evaporate different substances at different temperatures.

For example, in petroleum processing, fractional distillation is used.

Distillation. It is when the solution is heated to the boiling point.

Vaporization of the solution. The steam is then cooled to obtain a distilled liquid.

The distilled liquid is a pure substance with a certain degree of purity.

Evaporate. A method of precipitating crystals using evaporation solvents.

For example, evaporating copper sulfate solution.

It is to reduce the solvent in the copper sulfate solution.

This allows the copper sulfate crystals to precipitate.

Noodles are the distillation process, to put it simply:

1. To separate the liquid mixture, only when the boiling point of each component in the mixture is quite different, a more effective separation can be achieved.

2. Determine the boiling point of the pure compound.

3. Purification, by distilling substances containing a small amount of impurities, to improve their purity;

4** solvent, or evaporate part of the solvent to concentrate the solution.

Evaporation is a very common natural phenomenon.

But when the concept of "evaporation" is condensed as: "Evaporation is the evaporation of a solvent by heating to obtain a solid solute." At this time, I felt that the concept of evaporation had lost itself.

Teacher Zixu taught us that an important indicator of the reason why smart people are smart is: association.

Mention: the concept of evaporation, whether it can be associated with a beautiful rainbow after rain; Think of the blue sky, the white clouds; The beautiful illusion of a mirage; It is associated with drying salt with seawater; It is associated with drying clothes, boiling water, cooking rice, ......, has always been associated with a delicate flower that was picked after losing its moisture and evaporating from the world.

Let us enrich the association, let us have flesh and blood, fresh jump, and infinite vitality.

The concepts of evaporation, concentration, crystallization, and recrystallization are not difficult to understand in the specific scenario of coarse salt purification.

Evaporation: The operation of separating the difficult volatile solute from the solution and evaporating the volatile solvent. For example, the water in the solution of the remaining sedan chair in the brine of the food vertical is evaporated and the salt is crystallized.

Premise sodium chloride is difficult to volatile). Bromine iodine cannot be extracted from bromine iodine water by evaporation. (Liquid bromine is volatile, iodine can be sublimated.)

Instrumentation and operation of evaporation.

Note: The liquid poured into the evaporation dish is generally not able to evaporate 2 3 of the volume of the dish, and when it evaporates to near boiling, it is necessary to stir continuously with a glass rod to prevent the droplets from splashing due to excessive local temperature. When a large amount of solids appears in the evaporation dish, the heating is stopped and the residual heat continues to evaporate the remaining small amount of liquid until it is dry.

It is to separate the two substances, and if you want to get pure water, you can use the distillation method. Distillation flasks are used for distillation, and extraction flasks are used for extraction.

To put it simply, what is needed for distillation is what is steamed out (with a distillation flask), and what is needed for evaporation is what is left (with an evaporation dish).

1 dispensing for separating immiscible liquids.

2. Filtration, separation of solids and liquids.

3 Sublimation, separation of solid substances with large melting points (such as a common method for separating iodine and other solids in the dust mill).

4. Extraction, a solvent extracts solutes from the solution (conditions: two solvents are inmiscible; The solubility of the solute is very different between the two solvents).

5. Pyrolysis.

6 Distillation or fractionation, the separation of liquids dissolved in each other, the boiling point is quite different.

7. Salting-out, the process of precipitation of solutes due to the decrease in solubility in salt solution.

8. Recrystallization, cooling of the hot saturated solution many times.

9Dialysis, colloidal purification (semi-permeable membrane).

10. Wash gas.

It can be discussed according to one aspect of the chemical separation method. For example:

Extraction. Dispensing. Fractionation. Distillation. What are the conditions for which evaporation applies?

Extraction: suitable for a solute in two immiscible solvents in the solubility of the situation is very different, if you want to extract this solute from the solvent with less solubility, choose the extraction method, such as carbon tetrachloride and water are not miscible with each other, and carbon tetrachloride is easier to dissolve iodine than water, so you can use a separating funnel to extract iodine elements from saturated iodine water, dissolve into carbon tetrachloride, and then separate iodine and carbon tetrachloride by distillation.

In fact, "extraction" and "separation" are often used together, otherwise the solute cannot be separated. If necessary, it is also used in combination with "distillation", as in the case above, to completely separate the solute and solvent.

Dispensing: It is suitable for separating two liquids that are immiscible with large density differences. For example, a mixture of water and vegetable oil will be layered up and down after standing, with water in the lower layer and vegetable oil in the upper layer.

At this time, you can use a separating funnel to open the piston to the lower layer of water just when it runs out, and use a beaker to undertake; Open the glass stopper again and let the vegetable oil pour out of the mouth.

Fractionation: It is suitable for separating liquid mixtures with similar boiling points, such as petroleum is obtained by fractional distillation, which are important chemical products: gasoline, diesel, alcohol, etc.

Distillation: It is suitable for separating liquid mixtures with large differences in boiling points, and separating them in the order of boiling points from low to high by using the different boiling points of each component. or remove volatile, difficult to volatile or non-volatile impurities.

For example, the method of distillation is used to reduce the cl- impurities in tap water. Or separate the solvent in the solution, such as salt water by distillation to obtain purer distilled water.

Evaporation: It is suitable for separating volatile solvents and solutes in a solution, which is similar to the second case of "distillation" I said, but if you want to get pure table salt instead of water, evaporation is generally used instead of distillation. There is also what I call the combination of "extraction" and "evaporation".

In short, there are many chemical separation methods, and it is necessary to choose the appropriate method according to the situation, and some methods are interconnected, and the method should be selected in accordance with the principles of science, safety and simplicity.