Ink Chromatography
Forensic Lab Activity--Ink Chromatography
  1. Background Chromatography (Chroma=color and graphia=writing) is an ancient method used to separate and identify parts of a mixture. Ink is a mixture of several colors used to produce one. Using chromatography, the colors in ink can be separated. If ink is exposed to certain liquids, called solvents, the colors will dissolve and separate within the liquid. If the solution is then allowed to soak into a piece of chromatography paper, the different colors will created bands on the paper. They will remain in solution. Inks of the same type will always produce the same banding pattern when this technique is used. The resultant paper with bands on it is called a chromatograph.

    Procedure Case 96-337

    1. Sign and date the label on the evidence bag.

    2. Take out the piece of the note in Exhibit I. Place the strip of paper into the test tube. Make a mark on the test tube below where the ink is on the strip. It is important that the solvent you pour into the test tube is below the ink and just touches the bottom of the paper. Remove the strip and then pour in the solvent (water) Replace the strip.

    3. Take the pen that is Exhibit J. Make a dark band of ink on a piece of chromatography paper 2 cm from the bottom edge of the paper. Repeat the procedure as in number 2 above.

    4. Do the same procedure with ink from the pen in Exhibits K and L.

    5. Set the test tubes in a rack. Wait until the solvent no longer appears to be moving up the chromatography paper leaving color bands. Let the four papers dry and then tape them into the Lab Report form. Be sure to identify which is Exhibit I, J, K and L.



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