Students use chromatography to separate the colours in black ink.
The unique colours in different black pens can be used to identify which pen was used to write a note, showing how chromatography can be used in forensics.
Black pens are recommended because they usually have many different dyes in their ink. Students should be encouraged to try markers of different colors or food coloring (the green food coloring works well). Do not be disappointed if the marker does not produce a dramatic separation pattern.
Can black ink be separated by chromatography?
Chromatography is a method for analyzing mixtures by separating them into the chemicals from which they are made. It can be used to separate mixtures like ink, blood, gasoline, and lipstick.
Why shouldn t we use a black pen to make marks on the chromatography paper?
1) You can’t use a pen to mark the chromatography paper because the ink may dissolve in the solvent and contaminate the sample, affecting the results.
What happens to black ink in chromatography?
When the water passes through the black ink it takes the pigment colors with it. Some pigments dissolve in water easier and are pulled with the water farther up the paper. This is called chromatography – separating the parts of a mixture so that you can see them one at a time.
What liquid is best for chromatography?
Readily Available Solvents for Paper Chromatography
| Solvent | Polarity (arbitrary scale of 1-5) | Suitability |
|---|---|---|
| Rubbing alcohol (isopropyl type) | 3 – Medium polarity | Good |
| Vinegar | 3 – Medium polarity | Good |
| Nail polish remover (acetone) | 4 – Low polarity | Good |
| Turpentine | 5 – Least polar | Good |
Black ink is a mixture of three colours red, blue and green. These are the three different dyes which has the different affinity for the mobile phase used in the chromatography. All three dyes are separated on the travelling medium (filter paper) as the bands of different colours.
How many colors separated from the black ink? Five colors separated from the black ink: yellow, pink, red, purple, and blue.
You will get the best results with chromatography paper, however, since you need a substitute, try using paper towels. Use a plain white towel that has sturdy and dense texture. Coffee filters will not work.
What are the mistakes in paper chromatography?
Let them get it wrong
| Mistake | Problem caused |
|---|---|
| Incorrect solvent used | Ink insoluble so chromatography doesn’t occur. |
| Start line drawn in ink | Ink dissolves/runs in solvent. |
| Spots under the solvent | Ink will dissolve in the solvent and wash off the paper. |