Paper Chromatography

Dhristi JEE 2022-24

Paper Chromatography Definition

Separating components from a mixture is Chromatography. To start the process, a substance known as the mobile phase dissolves the mixture, which carries the same to the second phase, i.e., the stationary phase.


A mixture has different components that travel through the stationary phase at distinct speeds to get isolated from one another. The behavior of the specific mobile and stationary phases decides which substances to travel more quickly or slowly, and this is how they are separated. The travel time of the different components is retention time.


Vedantu has provided the notes on Paper Chromatography which is the part of chemistry. Paper Chromatography is a technique to separate the mixture components dissolved in the chemical using their varied migration rates across the sheets or papers.


Learn Method of Paper Chromatography and its Types

In the notes, experts have given a thorough explanation about the method of paper chromatography. It is a piece of straightforward information, which students can easily understand. Students can find that each step of the method is explained in detail by the Vedantu, which is helpful to them while reading for the exams or any competitive exam. The paper chromatography method is one of the most looked forward to separating the components like peptides, amino acids, steroids, and purines.  


Apart from the method, the subject matter expert of the chemistry has added the different types of paper chromatography in the notes. There are five types of paper chromatography, and experts have pulled down each type very precisely and accurately on the paper. So, students can gain a thorough knowledge of it. 


Paper Chromatography: Quick and Easy

Paper chromatography is a quick and easy process to conduct. Most of the time, it is used to test the purity of compounds and to identify substances. It requires only a few materials for carrying out the process.


Students can find the detailed reasons behind the widespread use of paper chromatography. Also, to give in-depth knowledge about these reasons, students can take a Vedantu online tuition where experts explain each topic in detail. 


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More About  Paper Chromatography

In analytical chemistry, paper chromatography is defined as a technique for separating dissolved chemical substances by taking advantage of their varied rates of migration across sheets of paper. It is an inexpensive method but a powerful analytical tool that needs very small quantities of the material.


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About Paper Chromatography Method

This method contains applying the sample or test solution as a spot near one corner of a sheet of the filter paper. Initially, this paper is impregnated with some quantity of suitable solvent to create a stationary liquid phase. An edge of the paper, which is close to the test spot, is then immersed in the other solvent, where the components of the mixture become soluble in differential degrees. The solvent also penetrates the paper by capillary action and, in passing over the sample spot, carries along with it the different components of the sample. These components move along with the flowing solvent at velocities, which are dependent on the solubilities present in the flowing and stationary solvents.


Separation of these components is brought if there are differences in the relative solubilities present in the two solvents. Prior to the flowing solvent reaching the farther paper edge, both the solvents are evaporated, and the location of the separated component can be identified, generally by the application of reagents that produce colored compounds with the separated substances. Then, the separated components appear as individual spots on the solvent’s path. If the solvent that is flowing in one direction is not able to separate all the components in a satisfactory manner, the paper can be turned 90°, and the process will be repeated using the other solvent.


The paper chromatography method has become a standard practice for the separation of complex mixtures of peptides, amino acids, steroids, carbohydrates, purines, and a long list of simple organic compounds. Also, the inorganic ions can readily be separated on paper.


Pigments and Polarity

Paper chromatography is a method that is used for testing the purity of compounds and the identification of substances. The paper chromatography method is a useful technique due to the reason it is relatively quick and needs only small quantities of material. Separations in the paper chromatography method involve the partition principle. In the method of paper chromatography, the substances are distributed between a mobile phase and a stationary phase.


The stationary phase is defined as the water trapped between the paper’s cellulose fibers. The mobile phase is defined as a developing solution, which travels up the stationary phase by carrying the samples with it. The sample components will readily separate as per how strongly they adsorb onto the stationary phase vs. how readily they dissolve in the mobile phase.


When a sample of colored chemical is placed on a filter paper, the colors get separated from the sample simply by placing one end of the paper in a solvent. Then, the solvent diffuses up the paper by dissolving the different molecules in the sample as per the polarities of the molecules and the solvent. If the sample has more than one color, it means it must contain more than one kind of molecule. Because of the various chemical structures of every kind of molecule, the chances are high that each molecule will have at least a slightly different polarity by giving each molecule a variable solubility in the solvent.


The unequal solubility causes the different color molecules to leave the solution at various places as the solvent continues to move the paper up. The more soluble a molecule, the higher it will migrate up the paper. The chemical will not dissolve in a very polar solvent if it is very non-polar. This is similar to a very polar chemical solvent and a very non-polar solvent.


It is also important to make a note that when using water (which is a more polar substance) as a solvent, when the color is more polar, it will rise higher on the papers.



Types of Paper Chromatography

Let us discuss the types of paper chromatography given below.

 

1. Descending Chromatography

Chromatogram development is done by allowing the solvent to travel down the paper. In this case, the mobile phase is placed in the solvent holder at the top. And, the spot is kept at the top, and solvent flows from top to bottom of the paper.

 

2. Ascending Paper Chromatography

In the ascending paper chromatography case, the solvent travels up the chromatography paper. Both the ascending and descending paper chromatography are used for the separation of both organic and inorganic substances. The solvent and sample move upward.

 

3. Ascending-Descending Chromatography

This is the hybrid type of both of the techniques given above. The upper part of the ascending chromatography is folded over a rod to allow the paper to become descending after the rod crossing.

 

4. Circular Chromatography

In radial chromatography or circular chromatography, a circular filter paper can be taken, and the sample is deposited at the paper’s center. After the spot gets dried, the filter paper can be tied horizontally on a Petri dish that contains a solvent so that the paper’s wick is dipped in the solvent. The solvent then rises through the wick, and the components get separated into concentric rings.

 

5. Two-Dimensional

In this particular technique, rectangular or square paper can be used. In this case, the sample is applied to one of the corners, and the development can be performed at a right angle to the direction of the first run.

FAQs on Paper Chromatography

1. What are the applications of paper chromatography?

Paper chromatography has multiple uses as it is a quick and easy process to study the dissolved components. Below you can find a list of fields where paper chromatography is widely preferred. 

  • To Separate Colour: It is a cost-effective technique that separates coloured pigments from a mixture. You can find this in the notes provided by Vedantu.

  • Pathology and Forensic Science: Forensic departments extensively use paper chromatography for solving crimes as this process needs small quantities of material. 

  • Food Industry: To improve the face of food and make it more popular among the public, most hotels prefer paper chromatography for analysing food colours in ice creams, drinks and jams, and jellies. Also, to ensure only permitted edible colours are added to the foods.

2. How does paper chromatography work?

Although the paper chromatography method is simple to process, it is not easy to explain compared with thin layer chromatography. The explanation concludes on what type of solvent we are using, and several sources gloss over the problem completely. If we have not already done so, it would be helpful to read about the explanation for how thin layer chromatography works. You can find more about the working of paper chromatography on the Vedantu website or download the Vedantu learning app from the play store to read about it on your mobile device.

3. Give the purpose of paper chromatography?

The paper chromatography method is an inexpensive and fairly rapid technique to gain a qualitative assessment of the mixture’s components. We can think of it as a “scouting” technique to gain insights into the effective use of the other chromatographic methods, both analytical and preparatory. The only purpose of paper chromatography, in general, is to split the molecules based on distinctions in size, polarity, and solubility. Paper chromatography uses paper as the stationary phase and a solvent as the mobile phase. The mobile phase travels through the stationary phase and molecules come out in a differential manner.

4. Why is water not used in paper chromatography?

When you talk about Paper chromatography, you should know that it is not a very precise technique, and it is pretty much limited to the demonstrations. And water is a highly polar molecule. It does not modify the polarity of the non-polar solvents.

 

Also, you can take an example of cellulose, which is polar, so there’s no difference between the water and cellulose to separate the compounds.  You can find more about this in the online classes of chemistry, where experts have explained it in detail.

5. How to download resources related to paper chromatography?

Vedantu provides you with a thorough explanation of the topic on their website, which you can read at any time from any device for free. Also, you can download the questions related to it from the study material section which is available on the website or the app. However, Vedantu also takes online tuition classes to help students understand the concepts readily with the help of three-dimensional illustrations. Signup with your genuine email id to access all these resources on our device.

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