Science Buddies: "Ask an Expert"

I have already done the experiment and found all the data, but I would like to find the amount of dye in each piece of candy. Is there a way to do this using the chromatography? If there is how would I do that? If not what is another method that I could use to find the amount of dye?

Thanks
Maria

This experiment uses a principal used very often in chemical analysis. It compares an unknown substance to a known substance. If there is a match, then you can determine what the unknown substance is.

In this case, you remove some unknown dye from a candy. You run a test on it - the chromatography test. Then you run the same test on several known dyes. Then you compare the results from the unknown sample to the results of the known samples. When you find a match, you know what dye was used in the unknown sample.

This comparison method can be used with allot of different chemical analysis methods. The DNA tests you see on TV crime shows is like this. They compare a sample with unknown DNA to a sample from someone who they know and look for a match.

But to answer your question, no you cannot measure the amount of dye using this method. You can only identify which dye was used. But you can use this information to determine the amount of dye used. One way I can think of to measure the amount of dye goes like this:

1) Using chromatography, determine what kind of dye is in the candy
2) Take a small sample of the candy and carefully weigh it
3) Completely dissolve it in water in a suitable clear container
4) In a separate identical container, add the same amount of water
5) Then add an amount of pure sugar that is the same weight as your candy sample - this will create a solution VERY similar to the one created by dissolving the candy in the water, because most candy is nearly all sugar
6) Now carefully add drops of the dye you identified that is the dye used in the candy to the sugar water, and make sure you measure those drops
7) When the color of the sugar water solution matches that of your sample of candy dissolved in the water, you can conclude the candy had the same amount of dye in it that you put into your sugar water

I hope this works for you.

Have fun!