Chromatography

Chromatography is a method of separating molecules based on size and rate of travel through a medium. For this week's Whodunnit class we used paper chromatography in order to identify which pen was used to sign the birth certificate of the fictional Princess Michaeala who had been kidnapped at birth. The Royal family managed to retain a portion of the original document and the kidnappers absconded with the rest of it. When a young woman resurfaced claiming to be the Princess (I likened it to the animated movie Anastasia that children would be familiar with) the torn document that she possessed would be tested against the existing piece in the Royal archives and the against the original pen used by the Registrar of Births.

Each student was provided with the following evidence sheet on which I had attached a strip of filter paper (coffee filter) with a sample of ink from the Registrar's pen which had been processed by chromatography. The students were then given three samples to test in order to find the matching ink pattern. In a clear plastic cup, I placed a half inch of acetone nail polish remover and the students placed their samples. We allowed the samples to rest for 10 minutes. The capillary action of the filter paper did the rest. Students removed their samples and placed them on wax paper (to protect desk surfaces) to dry. Then they compared the samples to the one provided and made a match. The documents in question were a match, no case of forgery. But is the Princess herself the real thing. That will bring us to the next topic, DNA testing.