paper chromatography to compare natural/store-bought markers

[yikes!]

We're having trouble getting the natural dyes from fruits/vegetables to stain dark enough. Blueberries worked. Pineapple was too light. Finely chopped spinach was too pale. Is there a trick to pigment extraction & which fruits/vegetables work best? Will coffee work? We are running out of time!

[deleted-3443]

Some random thoughts...

How about red beet juice? Stains nicely.

How are you extracting pigment now? Could you use less water to make a more concentrated ink? Could you try other solvents?

If you don't hold the pigment extraction method constant, does that change the meaning of the experiment?

Remember that unexpected results are still results. You can show that some of the inks did not work the way that you expected and collect data on them just the same. As Adam always says on Mythbusters: "Failure is ALWAYS an option." When things don't go as you expect, that's science! (In fact, surprises are often the most interesting kind of science.)

--Janet

[donnahardy2]

Hi,

This is a really great project idea from the Science Buddies website:

https://www.sciencebuddies.org/science- ... p014.shtml

Janet sounds like she is very experienced, and has given you a good suggestion the suggestion to use beets and the fact that science experiments don’t always turn out as expected.

The problem that you encountered is due to the chemistry of the dyes you are extracting from the plants:

Spinach contains mostly chlorophyll, which is a large molecule that is not soluble in water. Also, when heated, the chlorophyll changes structure and the plant pigment loses is bright green color. The project directions include boiling the plant sample in water, which is definitely not ideal for chlorophyll.

The yellow color in pineapple is due to pigments called carotenes. This is the same class of molecule that makes carrots orange. Like chlorophyll, carotenes are not very soluble in water, so it would be difficult to extract a concentration high enough to get a good result in this experiment.

Blueberries and beets contain pigments call anthocyanins, which are much more soluble in water. This allows extraction of a higher concentration of the plant pigment into water. If you do a Google search of the various plant pigments and look at the chemical structure, you will see that chlorophyll and carotene are composed mostly of carbon and hydrogen atoms; the anthocyanins also have more oxygen atoms, and if you look at the chemical structures, you will see some OH (hydroxyl groups) present. The oxygen atoms make the anthocyanins much more soluble in water compared to chlorophyll and cartotenes. If you will Google “plants with anthocyanins,” you will find the names of lots of other plants that will work well in this experiment. It is always difficult to obtain extracts of plant dyes that are really intense, so make your samples as concentrated as possible

I hope this will help you understand more about the science behind your project. It will be important for you to present the results of the spinach and pineapple samples and explain what happened. Please do let me know if you need more explanation about the chemistry of this project.

Also, after you have finished this project, please go to the Science Buddies Home Page, and click on the “My Science Buddies Tab.” Select, “I did this project,” and give us your feedback on the project idea.

Good luck!


Donna Hardy