SUCCEED

Ink Chromatography Lab

Objective: Students will learn about forensic analysis through the chemistry of solvents, solutes, and the bonding natures of different inks.

Materials: Each student will need

• samples of black and blue pens
• coffee filters cut into strips
• skewers or other long objects
• pans that can hold 1/2" of liquid
• paper and pencils

Overview

Chromatography is a method of separating out materials from a mixture. Ink is a mixture of several dyes and therefore we can separate those colors from one another using chromatography. When ink is exposed to certain solvents the colors dissolve and can be separated out. When we expose a piece of paper with ink on it to a solvent, the ink spreads across the paper when the ink dissolves.

Some inks are water-soluble, so you can use water as the solvent. Inks which are not water soluble are often alcohol-soluble and you can use Isopropyl alcohol as the solvent to create your chromatograph.

Different ink pens use different types of ink and this is obvious when you expose the ink to a solvent. A banding pattern of the components of the ink mixture is called a chromatograph. Follow the instructions below to discover which pen was used to write a note.

Directions

1. Gather several black or blue pens
2. Obtain a sample of the evidence (have someone use one of the pens to write a note - your job is to figure out which pen they used)
3. Cut several coffee filters into 1/2" strips
4. Set up your chromatography apparatus. Place a skewer or other long object across two supports. Place a pan underneath the skewer and fill it about 1/2" deep with the solvent (water or alcohol).
5. Use a long 1/2" wide strip of your evidence and hang it from the skewer so that the end just touches the solvent. Don't let the ink get wet.
6. Use each of your suspect pens to place a dark spot of ink about 1/4" - 1/2" from the end of each coffee filter strip.
7. Hang these strips from the skewer so that the tips of the strips just touch the solvent
8. Allow the inks to separate for about 15 minutes
9. Examine the banding patterns and determine which of your known suspect pens is the pen used to write the note.