Paper Chromatography- Types, Forensic Significance, Advantages, and Disadvantages

Paper Chromatography is a separation technique in which a substance mixture is separated based on the partition or adsorption principle where cellulose paper is a stationary phase while the solvent is the mobile phase.

Paper chromatography is used particularly for separation of lipid samples and chemical substances.

Types of Paper Chromatography

Paper Chromatography has been classified into 5 types. These are:-

1. Ascending Chromatography
2. Descending Chromatography
3. Ascending-Descending Chromatography
4. Radial Chromatography
5. 2-D Chromatography

Ascending Chromatography

In this type of Chromatography, the development of chromatogram is done by allowing the mobile phase to run in the upwards direction on the stationary phase. In this method, the solvent is at the bottom of the chamber while the stationary phase is dipped in the chamber with the sample spot just above the solvent.

This technique is used for the separation of organic and inorganic substances.

Descending Chromatography

In this type of Chromatography, the solvent runs in a downward direction. The solvent is kept at the top of the chamber and the paper is attached to it. The solvent runs down the paper due to gravity rather than capillary action.

The advantage of this chromatography is that the development of chromatogram runs indefinitely even if the solvent runs off at the other end. It is used for the separation of organic and inorganic substances.

Ascending-Descending Chromatography

This technique is the hybrid of two techniques i.e., Ascending and Descending chromatography.

In this technique, the upper portion of the ascending is rolled over glass rod to change into descending after rolling over the rod. Initially, the solvent runs in the upwards direction and then after crossing the rod moves in downward direction.

Radial Chromatography

This technique is also known as the circular chromatography. In this technique, a circular paper is used as a stationary phase which is placed over the petri-dish where the mobile phase is kept. The paper is connected with the solvent through a wick from where the solvent runs towards the periphery.

The chromatogram is developed in the form of concentric circles.

Two-Dimensional Chromatography

This type of paper chromatography is done on a square or rectangular paper. The sample is applied at one corner of the paper and the solvent is then run through the paper.

After the development of the chromatogram, the paper is dried and rotated at an angle of 90 degrees. The separated components will now be separated through the same or different solvent used.

Forensic Significance of Paper Chromatography

• For separation of components of the ink.
• For separation of amino acids.
• To detect any kind of adulteration in foods & drinks.
• To determine drugs in humans and animals.

Advantages of Paper Chromatography

• It is Cheaper and quite simpler than other techniques.
• It is less time-consuming.
• Requires a very less amount of sample for testing.
• It is quite easy to set up and handle.
• Both organic & Inorganic substances can be separated using Paper Chromatography.
• High-Sensitivity.

Disadvantages of Paper Chromatography

• Separation of complex mixtures is difficult.
• It is not compatible with testing large amounts of samples.
• This technique is not suitable for the separation of volatile substances such as hydrocarbons and volatile fatty acids.
• Not suitable for quantitative analysis.
• Not as accurate as HPLC and TLC.
• Chromatograms cannot be saved for a longer period of time.