Paper chromatography has a large range of uses. It was “rediscovered” ten years ago and its possible uses seems to grow rapidly. It is a laboratory test to help discover the components of a substance. This can come in handy in many situations.
Interestingly this is one of very few scientific processes that through the years has not needed to be improved upon. It has been studied extensively and for the most part remains the same. In this article you will learn the definition, process and purpose of paper chromatography. (4, 5, 10)
What is Paper Chromatography : Definition
It is basically a method used to separate the components of a particular substance. The prefix of Chromo means color and -graphy means writing so it technically means writing in color. When you see the process you can understand why the name was given. (1,2,7)
Principles of Paper Chromatography
Some of the key factors in chromatography are:
- Pigment solubility
- Paper attractively- this can depend on surface adsorption, ion exchange or partition between the solvents.
- The behavior when placed in ultraviolet light.
- Nature of the color and substance
- Detection of radioactivity(2,3,5)
Some liquids can be converted into colors in order to help identify the specific percentages of its make up.(3)
Certain rules should always be observed when doing a paper chromatography test.
- The flowing solvent composition should remain the same through the development.
- The type of paper and width of the wick should also remain the same.
- The components should be soluble with the solvent used.
Picture 1 : A clear example of the chromatography process.
Photo Source : www.bbc.co.uk
How does Paper Chromatography work
The paper is a solid in which the liquids pass through. Adsorption happens which is the adhesion of molecules from the liquid to the surface of the solid. This is very different from absorption. Each solution inside the liquid will adsorb at a different speed.
One will travel slower and therefore not as far as one that travels faster. The slower moving liquids could be said to sick easier to the solid.
The site explainthatstuff.com has made a drawing which helps to understand this process. (4, 7, 10)
Image 2 : Flow of specific type of molecule through the paper.
Picture Source : cdn4.explainthatstuff.com
Paper Chromatography experiment
The following video shows a fun representation of what chromatography is and how youc can esily do an experiment at home.
Photo 3 : This is how the process begins.
Image Source : www.chemguide.co.uk
Image 4 : In this image you can see how the level of solvent should not touch the pencil line.
Picture Source : www.chemguide.co.uk
Figure 5 : Here the test is finished and shows the different levels of the solutions in each specimen tested.
Photo Source : www.chemguide.co.uk
Phases of Chromatography
Basically a substance is placed on paper and when a solvent is added the substances will be begin to separate and show the different particles inside the substance. (1, 7, 10)
Paper Chromatography stationary phase
The stationary phase is when the original substance is flowing through the paper and is beginning to separate. In this stage you can even evaluate the speed in which each component moves in the paper. The molecular weight can be determined by evaluating the speed. (2, 10)
Advantages of Paper Chromatography
- Helps to compare solutions and percentages of components in each solution.
- Is very specific
- Provides chemical identity
- Can be roughly or highly quantitative
- Active fraction is easy to trace
- Does not need a large amount of sample saving any extra sample for other types of testing.(3,7)
Chromatography can be considered very useful for multiple reasons. Below is a list of some of these reasons.
- It is easy
- It is fast
- Requires only small amount of specimen (2,6)
Chromatography is a laboratory process used on a daily basis. Although most people may not have heard of the name in is common practice in many careers. The following are examples of how paper chromatography is used.
- Drug mixtures- Illigal as well as legal drugs can be broken down into its true substance to better understand how, who and where certain drugs were made.
- Paint mixtures- This can help to find a certain make and model of cars involved in accidents.
- Analyzing amounts of Drugs in the blood stream– Useful during poisonings or overdoses.
- Horse meat? – There has been many issues in the food and drug industry causing court trials. In these trials paper chromatography is used to decide the make-up of the foods. This has proven for example that meat that had been sold had horse product in it.
Finding and defining disease carriers.
- Ebola (1,5)
Paper Chromatography lab
This video shows the proper method of how to do Thin-layer paper chromotagraphy TLC.
Paper chromatography is not the only type of chromatography here is a list of other types:
- Column chromatography
- Gas chromatograph (4,7)
Different methods are used in the Paper Chromatography.
- Kapilaranalyse- best used to separate pigments in plants, fats, alkaloids as well as impurities from food products.
- Descending Chromatography- The upper end of the paper is put into the solvent and is hung in a chamber that is air tight.
- Ascending Chromatography- the solvent is at the bottom of the paper and is easier to do correctly than descending chromatography.
- Ascending-Descending Chromatography- Hung in a way that the solvent goes up one side and down the other.
- Filter paper “Chromatipoile”- Makes a sort of assembly line in order to large quantities of substance.
- Reversed Phase- Uses rubber latex and has a dry, rinse and store process.
- Circular Filter paper Chromatography- In this type the techniques ends up having a circulatory zone instead of columns and bands.
- Microbiological and enzymatic methods- used for vitamins as well as antibiotics.
- Paper Electrophoreses- separation is made due to the polarization of the molecules. (5, 6)
- Paper Chromatography: A Laboratory Manual By Richard J. Block, Raymond Le Strange, Gunter Zweig https://books.google.com.mx/books?id=tS8XBQAAQBAJ&printsec=frontcover&dq=Paper+chromatography&hl=en&sa=X&redir_esc=y#v=onepage&q=Paper%20chromatography&f=false