Literature Review

Have you ever looked on the back of an M&M’s packet and seen a long list of different dyes and colors that you’ve never heard of before?  On the back of the wrapper, the label states all of the dyes that are used to color the candy, but which dyes are used in which colors?  Our topic is on candy chromatography.  Chromatography is a technique used to separate the various components in a complex mixture or solution.  We chose this topic because we wanted to find out which kinds of dyes could be found in different candy products such as M&M’s and Skittles. We also wanted to see if different products used the same color dyes or if they used different ones.

            In chromatography, water and filter paper are used to help the molecules of the dye to move. As the water travels through the filter paper, it picks up the dye particles and carries them along.  Chromatography works because substances differ in their ability to “stick” to other things. There are usually two stages of chromatography: the stationary phase and the mobile phase.  In this specific experiment, the candy is the stationary phase, and the water is the mobile phase. By putting drops of water on candies with different colors, we will be making the solution, which we will be testing.

            An example of a classic experiment may be paper chromatography.  In paper chromatography, the ink on the paper would be the stationary phase, and some sort of solution “washing out” the ink would be the mobile phase.  As the solution is being absorbed into the fibers of the paper – by capillary action – the water travels through the paper, picking up ink particles, and carrying them along.  Another example of a classic experiment may be glass chromatography, in which you fill glass columns with tiny, inert beads. In glass chromatography, the tiny, inert beads would be the stationary phase, while the solution used to “wash out” the mixture is the mobile phase.  In this experiment, the separation of the mixture added to the column, is based on molecular size.  The smaller the size of the molecule, the easier it is to pass through the spaces between the beads, resulting in them coming out of the column quicker.  The larger the size of the molecule, the more difficult and time consuming it is for it to pass between the beads; resulting in them coming out of the column later.  You can separate the smaller and larger molecules by collecting the liquid that comes off the column in a series of separate containers.

            The only current experiment of chromatography that we could find was the one that we’re doing: candy chromatography. In candy chromatography, you mix each differently colored piece of candy in a little bit of water to make the dye come off. Then, using a toothpick you continuously put dye on filter paper until the color on the paper is the same color as the candy.

            In conclusion, what we hope to learn from this experiment are the different dyes that are used to color different candies.  Some of the uncontrolled variables of this experiment are the timing; each candy that we put in the little bit of water may not be in for the same periods of time.  Not only learning what the different dye of each candy is, but also we would like to learn the other ingredients that are combined within it.