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Paper Chromatography Experiment

What if I told you, that you can separate colors, with just water and blotting paper, using a fun experiment called paper chromatography. In this article you will find out the purpose of paper chromatography experiment, the principles of chromatography, and a stepwise procedure to perform paper chromatography hands-on!

Paper Chromatography using ink
Paper Chromatography using ink. Image Credit_Manylabs Archive

What is Chromatography ?

Chromatography is a technique that is used to separate colored substances. (kroma = colour; graphia = graph). It involves two components, a mobile phase, which is the solvent(eg: water) that dissolves the colored substance, and carries it through the stationary phase, which is the fixed medium up which the color-solvent mixture rises(eg: blotting paper). When paper is used as the stationary phase, it is known as paper chromatography.

Plant pigments separated by paper chromatography
Plant pigments separated by paper chromatography. Image Credit_Stefen Walkowski

What is the purpose of Chromatography ?

Chromatography is widely used in both research and industrial field. Some fields that makes extensive use of chromatography are:

·         Forensic scientists(scientists who perform tests on samples collected from crime scenes) use chromatography to analyze blood and cloth samples.

·          The beverage industry use chromatography to check and maintain consistent taste of their product.

·         The pharmaceutical industry use chromatography to extract pure forms of enzymes, proteins and medicinal ingredient.

 

·         Vaccines like Zmapp, that is used to fight Ebola, are developed using chromatography.

Chromatography in vaccine development
Chromatography in vaccine development. Credit_Sola Charles (Twitter)

The procedure for paper chromatography experiment :

Materials :

  • 4 strips of paper towels (0.8 in x 4 in)  
  • Cup of water 
  • Black markers or Sharpies of different brands 
  • Pencil 
  •  Binder Clips

Steps to follow :

  1. Cut out strips of 2 cm (0.8″) x 10.5 cm (4.1″) from the blotting paper/tissue paper.
  2. Draw a line 0.6 in (1.5) cm from one edge to other using a sketch pen.
  3. Place a pencil into the binder clip, and hold the paper strip using the clip. The black marker line is on the other end. This is one method to hold the paper strip. You could also use a simple paper tape and pencil.
  4. Fill the cup with water, 0.8 in (2cm) from the bottom.
  5. Place the pencil with the strip over the cup such that the tip of the paper strip submerges into the water. Make sure that the line drawn by the marker does not submerge. Keep the setup undisturbed for five to fifteen minutes .
  6. Repeat experiment with other brands of black markers. Compare the colors between them. Are all black markers the same?
paper chromatography experiment
Chromatography Setup. Credit_NoelPauller

Basic Principle of Paper Chromatography :

Although sketch pen ink might look like it is comprised of single color, it actually isn’t. Simple black ink in a sketch pen is a combination of red, blue and green dyes mixed in water. These dyes have different densities, which indicates how heavy the dye is. When the strip with the water-soluble ink spot is lowered into the jar of water, the water starts to rise along the strip, and carries the dissolved ink with it. As the ink rises, heavier dyes rise slower than the lighter ones, producing a band of colors with the lightest dye on top, and the heaviest at the bottom.

Chromatography is a vital yet simple process. With newer techniques, better methods and more applications of chromatography will be found. As an extremely flexible process, chromatography might be the DIY test to check  presence of adulterants, or contamination in food, or check the various proportions of food coloring present in a food item. With people acknowledging the importance of food safety, chromatography will be a common household experiment soon.

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