Love those Flinn Fax - Chromatography

Chromatography sample set up

Earlier this school year as I was planning out my lesson on matter for my science seminar class, along comes the Flinn Scientific -Flinn Fax flyer in my school mailbox. What perfect timing! I had planned on doing chromatography, a method for separating mixtures, and here is a nice new twist on the technique.



Sample set up

I started the students on day one with simply asking them to set up a test paper with all the different brands of pens that I had available. The following day I gave them designs to copy. They had to use their findings to determine which pens to use. Everyone was successful as you can see by the pictures below. In the future I might even use different solvents to see if they can get results that differ from those they got here (we used water as our solvent but I gave them both water soluble and non-soluble pens).

Chromatography samples running

 I am continually amazed by what activities students are most fascinated by. This one was a huge success. Many simply tried to make interesting patterns of their own.




Student Sample 1

I placed my samples in plastic bags so that they wouldn't get wet. You can see here the student's work to copy my example.  I will now have these samples to use again next year which will save me a lot of preparation time.

Student Sample 2

Included in this photo you can see the sample disks that the students had completed on day one which show the pigment patterns generated by each type of pen available for use.

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.