Many people are unaware of what chromatography is and how it works. There are different chromatography types, such as liquid chromatography, gas chromatography, thin-layer chromatography, and paper chromatography. It can be challenging to understand each of them in-depth; hence today, our primary focus will be on the uses and types of paper chromatography.
What is paper chromatography?
Paper chromatography is a useful analytical tool. It is used to separate mixtures from different substances into their components. The Paper Chromatography is made up of different layers, and each layer allows different types of the compound to pass through it. In short, it is like a filter.
Additionally, qualitative and quantitative analysis of organic and inorganic samples are both performed using the chromatography technique. The principal of the chromatography process is made up of the stationary phase and the mobile phase.
As different components travel at different rates, the researcher can determine the analysis goals being made, for example, the density of colors.
Uses of chromatography
Separating Colored Pigments
Paper Chromatography is widely used for separating colored pigments. The mixture of the colored pigments is placed on the paper and then slowly immersed into a particular solvent.
As the molecules of the mixture dissolve, they isolate from the pigment. The pigments go to different layers on the paper chromatography as it has a different polarity. This application of paper chromatography is also called qualitative analysis.
When using paper chromatography, impurities can be identified and removed from compounds. It is also the method to test the purity of a substance. During the chromatography process, spots are likely to be formed on the paper.
The spots are identified, and by analyzing the number of spots created and the distance between the spots, the impurity can be determined.
Paper chromatography is helpful for the investigation of crimes. Samples such as DNA and fingerprints are collected from crime scenes for analysis at forensic labs. The forensic labs utilize chromatography paper to detect the presence of blood chemicals and alcohol.
There are many more uses of paper chromatography like identification of unknown compounds from mixtures, an inspection of cosmetics, identification of contaminants in drinks and foods, verification of dopes and drugs in humans and animals, detection of pollutants, and to analyze different compounds in pharmaceutical products.
Below are the 5 main types of paper chromatography
1. Descending Chromatography
Like its name, when using the descending chromatography, the solvents move downward on the paper. While using descending chromatography, the mobile phase moves downwards by gravity. Even though the setup is more complicated, the result of the separation is faster.
2. Ascending Chromatography
In ascending chromatography, the solvents move in an upward direction. Since the movement goes against gravity, this method takes much more time. However, the setup is much easier compared to the descending chromatography method.
3. Ascending – Descending Chromatography
This type of chromatography combines both the ascending chromatography and the descending chromatography. Therefore, while using the ascending-descending chromatography method, the solvent moves in the upwards and downwards direction at the same time.
4. Radial Chromatography
An analyte needs to be placed in a paper’s center to do radial chromatography, also known as circular chromatography. The paper is then placed on a petri dish that contains the solvent. Afterward, the wick of the paper is dipped in the solvent. During this process, you can observe circular sample spots being formed through the radial chromatography technique.
5. Two-dimensional chromatography
In two-dimensional chromatography, the paper is either in square or rectangle shape. The samples are placed at one corner of the paper, and during the process, spots being formed at right angles can be observed.
Try the below experiment at home
Anyone can try the paper chromatography experiment at home. Follow the below steps to do this experiment.
You will need the below materials:
- Chromatography paper
- Pens or Markers from different brands and of various colors
- Clear plastic cups
You are ready to get started:
- Mark a dot about ½” from the bottom of a chromatography paper with the desired pen or marker. You can choose various strips of paper. Or on the same paper, you can mark different colored dots.
- Pour water into a plastic cup. Make sure the water level is also ½”. The marker or pen dots should be equal to the water level.
- You can start observing how the color climbs up the strips. For example, if your dot is of black ink, you will be able to witness different colors other than black spreading on the chromatography paper.
To summarise, understanding paper chromatography in technical terms might be challenging. But, when you choose to do experiments, everything will be more explicit.