A technique is known as chromatography, which is a term taken from the Greek language & means “written in color,” will be used to separate the substances into their various colors. This is exactly the same technique that a “real” crime lab would use to determine the manufacturer of the ink used in a note found at the crime scene or later sent in as a ransom note.
To separate the substance into its components a piece of filter paper is used. The idea is to put a fairly small dot of the substance to be tested about 2 cm up from one edge of the paper. The bottom of the paper is then dipped into a liquid of some sort, such that the liquid level is below the level of the dot. The liquid is chosen such that it will dissolve the substances that make up the color. The liquid will travel up the paper, dissolve the colors, and drag them along as the liquid continues to travel up the paper. Since the molecules making up the colors are of different sizes and hence different weights and different dissolving properties, they will migrate up the paper at different rates. This will then separate them into their various components. These signature chromatograms can then be compared with knowns to determine the unknown.
1. Take a piece of filter paper and use a pencil to draw a line about 2 cm from the bottom edge of 1 long-side. You must use a pencil because it will not have an interaction with the water.
2. You will be testing 7 pens and on this filter paper and you don't want the samples to blend together. You are going to fold the paper in half, 3 times. This will ensure equal spacing for the ink samples. The folds are represented by the oranges dashed lines.
3. Using a pencil label each fold with the letter representing each of the markers. Example: A, B, C....
4. Place small ink dots of each of the known markers you are to test on the folds and along the line you just drew. Be sure to use the correct marker with the appropriate label. Marker A ink dot, placed on fold A, etc.
5. Put about 20 mL of water in a Petri dish.
6. Set your chromatography paper in the dish with the ink dot side down. Be sure the water level in the Petri dish does not touch any of the dots on the line you made.
7. The chromatograms are done when the water level gets up to about 1 cm from the top.
8. Take the chromatogram out and lay it on a paper towel to dry.
9. Match up your known “Crime Scene” chromatogram with the one already done, "The Unknowns."
10. Record in pencil on your chromatogram the "The Unknowns" number next to the marker it matches.
11. Using Pro Prof match the "Crime Scene" chromatogram with "The Unknowns."
12. Place your names on the chromatogram, and submit it to your teacher.