Paper Chromatography

Chromatography is a method for analyzing complex mixtures (such as ink) by separating them into the chemicals from which they are made. Chromatography is used to separate and identify all sorts of substances in police work. Drugs from narcotics to aspirin can be identified in urine and blood samples, often with the aid of chromatography.

Materials

• Paper coffee filters or paper towels • One  or more black permanent pen or marker (like a "Sharpie") • 2 or more black "washable" pens or markers (water solubale) • 3 Different colored pens or markers (ex red, green, orange, etc - try to get a good variety of washable & permanent markers) • Container full of water • Several sheets of paper • Small glasses or plastic containers • Isopropyl rubbing alcohol* or fingernail polish remover** • Pencils • Tape • Scissors • Stapler **Be aware that fingernail polish may damage some plastics and some lacquer finishes.  Use glass or ceramic containers. * Read and obey warnings on rubbing alcohol  and fingernail polish label.

Instructions

Part I - Separating Black Ink 1. Cut several coffee filters into long strips, one strip per pen. 2. Fold the end of each strip over then staple it to form a loop. 3. Place a dot of ink from each marker/pen near the bottom of each strip. Use a pencil to identify which strip belongs to which marker. 4. Poke a pencil through one of the loops you just made. Use the pencil to suspend the strip in a small glass or container. 5. Carefully add water to the glass until it reaches the bottom of the paper strip just below the ink dot. Be sure the ink stays above the water and the paper stays in the water. 6. Allow the water to soak up the strip and watch what happens to the ink drop. 7. Repeat this process using rubbing alcohol or fingernail polish remover instead of water for each strip and compare your results. 8. Let the strips dry and tape them on a sheet of paper as a record of the different pen types. Part 2- Secret Note Challenge 1. Turn your back while someone uses one of the pens you just tested to write a secret note on a piece of coffee filter. 2. Cut out several individual letters from the note. 3. Staple each letter to the bottom of a strip of coffee filter. 4. Conduct the chromatography experiment above to determine which pen was used to write the secret note. (Watch how the ink spreads up the paper. Compare it to your known samples of ink.)

Lab Analysis

Click here to print out a copy of the Chromatography Lab Report Sheet. This sheet has questions for you to answer about this experiment to turn in for CLC Points.

Copyright © 2003 Peter Piper Publishing Inc. Last updated April 14, 2003.