To mark the blog’s fifth birthday, Bart celebrates by reminiscing about how he was introduced to chromatography and sharing some fun chromatography experiments that can be performed at home.

I will always remember the first time I learned about chromatography . Like many chemists before and after me, I was introduced to chromatography by my chemistry teacher, who told me the story of the inventor of chromatography, Mikhail Tsvet.

I am always amused when people’s names match their occupations, such as Andrew Drinkwater, who works for the Water Research Centre. Then there’s Dr. Seawright, the Eye Specialist, and the Lawyer, Sue Yoo; there is even a book about the Arctic by Mr. Snowman. The same is the case for the inventor of chromatography, as the translation of Tsvet is color or bloom. An apt name for the person responsible for creating a technique for separating plant pigments.

As a botanist, Mikhail Tsvet was fascinated by the pigmentation of plants: the color of blooms! During the late 1800’s it was believed that two pigments contributed to the color of leaves, namely, chlorophyll and xanthophyll. Tsvet conducted several experiments that would form the basis of what would become known as absorptive chromatography. Tsvet coined the term chromatography, which he derived from two Greek words; chroma or ‘color’ and graphein, meaning ‘to write’. Tsvet’s breakthrough happened when he extracted some leaves and flowed this extract through a vertical open glass column that contained calcium carbonate using a combination of petroleum ether and ethanol. It was at this moment that something miraculous happened. The colors quite literally bloomed. The chlorophyll was separated into two bands, revealing two forms of chlorophyll. The experiment also resulted in eight additional bands found to be different pigments that also attributed to the color of the leaves.

This chromatographic method for separating a mixture into its components has been developed and improved over the years. It was later discovered that other things could be used for the separation, such as gases or even supercritical fluids . Nowadays, it is possible to separate far more than pigments in leaves. Still, basic principles put into practice by Tsvet remain the basis of all chromatography. Essentially a mixture is dissolved in a liquid (or gas/supercritical fluid) called a mobile phase. This is carried through a system (column, capillary tube, plate, or sheet) on which a stationary phase is fixed. As the different constituents of the mixture being analyzed have different affinities, they are retained for different lengths of time depending on how they interact with the surface, causing them to separate.

As with most things in life, they are easier to understand when you witness them first-hand. So, if you have children, or like me, you are young at heart, here is a fun experiment you can perform in the comfort of your own home that will introduce you to the concepts of chromatography.

Chromatography Butterflies

For this experiment, you will need the following:

• Non-permanent marker pens (or permanent – read to the end!)
• White coffee filters
• Small cups of water
• Pipe cleaners (or string)

Method

   1. Pick a marker pen of a specific color (hint: black, brown, and purple work well).

   2. Now draw a thick circle around the middle of the coffee filter (where the frilled edge meets the flat center).

   3. Fold the marked coffee filter in half, then in half again. You should have a cone/triangle shape with your pen marking in the middle.

   4. Fill the small cup with lukewarm water

   5. Slightly pull apart the coffee filter so that you can balance it on the glass with only the tip submerged in the water (Do NOT let the marker circle go in the water!).

   6. Let the coffee filter sit and watch what happens as the water begins to flow up the paper.

If all goes according to plan, you should now witness, just as Mikhail Tsvet did, that the mixture (the ink) is separating into its constituent colors.

   7. Once the mobile phase – the water – has reached the top, you can unfold your coffee filter to let it dry.

   8. Once dry, you can scrunch up the middle and fan out the sides – creating a colorful butterfly.

   9. Wrap a pipe cleaner around the middle (or use string) to hold the butterfly shape.

You can now test all your different colored markers to see what constituent pigments make up their color. You can also see what effect the temperature of the water makes on the experiment!.

Different dyes in ink travel through the chromatography filter paper at different speeds. The most soluble colours dissolve and travel further and faster than less soluble dyes which stick to the paper more.

The reason for using non-permanent markers is that these inks can be absorbed by water. Permanent markers are not soluble in water – this is what makes them permanent markers; that is not to say that the inks in permanent markers cannot be used in such an experiment. If you want to separate the components in permanent marker ink, you can use isopropanol instead of water. This highlights why different mobile phases must be used to separate different components.

I hope you enjoyed this introduction to chromatography whether you are 5 years old, like this blog, or if you are as old as me, which is umm errrr…

Till next time,