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Spring SAVY 2017, Day 1- Chromatography 101

Posted by on Tuesday, January 31, 2017 in Grade 5, Grade 6, SAVY.

We had a wonderful first day of SAVY discussing the practical uses and basic components of chromatographic systems. Chromatography is used to separate complex mixtures of molecules/chemicals into their individual components. As a class, we brainstormed reasons why people in various professions might want to use this technique. We developed quite the list, ranging from forensic experts who want to analyze trace evidence (inks, dyes, chemicals) to hospital room physicians who are trying to assess what drugs or medicines are present in a person’s body to pharmaceutical scientists who are attempting to isolate a specific compound from plants. While the uses and different types of chromatography vary widely, the basic components of chromatographic systems are the same. There is a stationary phase, an immobile material to which the mixture to be separated is adsorbed, a mobile phase which moves across the stationary phase to promote separation of the mixture, and some method of detection to visualize the results. Each week we will be exploring a different type of chromatographic system and using it to solve a real-world problem.

This week’s problem was entitled “The Case of the Altered Check.” The students were tasked with determining if an extra zero had been added to the end of the monetary number for which the check had been written (i.e. if “$50” had been altered to “$500”) and, if so, which suspect and his/her black pen had done the deed. For this problem, paper chromatography was used to separate individual pigments in each black ink. I encourage you to discuss with your student how they designed their experiment to solve this problem. Some useful discussion-starter questions follow:

  • In paper chromatography, what serves as the stationary phase? What was used as the mobile phase? How were the results detected?
  • How was the check analyzed to determine if the number had been altered?
  • Describe or depict the results. What conclusions can you make about the relative affinity of each of the components of the inks for the stationary phase and mobile phase?

We concluded by discussing the limitations of ink evidence and the assumptions inherent in our analysis. The students rightly pointed out that other information could probably be gleaned from the check itself and described some other pieces of evidence that they would seek to gather to support their claims. Consider asking your child what additional evidence they think would be important in order to convict the correct culprit.

I’m already looking forward to next weekend when we will encounter a new problem and use a different chromatographic technique to solve it!



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