Chromatography for Your Kids

One of Agilent’s most fundamental technologies is our ability to measure molecules.  Customers want to analyze samples that can range from blood serum to metal ores to drinking water to crude oil to pharmaceutical compounds.  They want to know “What’s in there?” as well as “How much of it is there?”

The first thing an Agilent instrument would do is separate the sample into its individual molecular components, so that each one can be analyzed separately.  One method for doing this is called “chromatography.”  Gas chromatography is good for separating smaller molecules typically found in chemical substances.  Liquid chromatography is good for separating larger molecules typically found in biological substances.

“Chromatography” comes from the Greek for “color writing.”  Think of how a prism separates white light into different colors.

Agilent’s Jim Hollenhorst shares an experiment you can do at home to demonstrate how chromatography works.  You will need three pieces of “scientific equipment”:

  • A felt-tip pen, preferably black
  • A piece of paper cut from a coffee filter
  • A beaker of water or rubbing alcohol (you can use a glass, but your children will be much more impressed if you call it a “beaker”)

Take the felt-tip pen and make a little spot on the filter paper. Then, hang the filter paper so the end is in the rubbing alcohol and the ink spot is just above the liquid. The alcohol will start to wick. If life is good, the chemicals will separate out and you will see different colors as the rubbing alcohol moves up the filter paper.


141106 Paper_chromatography

This happens because the various pigment molecules have different affinities for the paper and for the alcohol. The molecules move back and forth, sometimes sticking to the paper and sometimes flowing with the alcohol. If they don’t dissolve in the alcohol at all, they’ll stay at the starting point.

You can experiment with different pens and solvents to see what works best.  Impress your children!  Have fun!

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