Solution Science: Candy Chromatography
Do you have a favorite M&Ms or Skittle candy color? Have you ever wondered what dyes are used to make that particular color? Some candies are the color they are because of a single food coloring, while others may use a couple different dyes to create just the right appearance. In this activity you’ll get to do some scientific detective work at home to investigate which colored M&M’s candies use which dyes. If you have some M&M’s leftover from Easter, this is a way to put those candies to good, scientific use!
This activity is not appropriate for use as a science fair project. Good science fair projects have a stronger focus on controlling variables, taking accurate measurements, and analyzing data. To find a science fair project that is just right for you, browse our library of over 1,200 Science Fair Project Ideas or use the Topic Selection Wizard to get a personalized project recommendation.
If you’ve ever seen a drop of water hit a print-out from an inkjet printer, you know that when this happens the ink starts to run. The water is absorbed into the fibers of the paper by capillary action. As the water travels through the paper, it picks up ink particles and carries them along. This same process can be put to good use as a technique called paper chromatography.
Chromatography includes a group of techniques that are used to separate various components in a complex solution. In each chromatography apparatus, there is generally a mobile phase (which is a fluid the components are dissolved in) and a stationary phase (which is the material the fluid moves through). For example, in paper chromatography, water is the mobile phase and paper is the stationary phase. The solution’s components ideally move at different speeds as they travel through the stationary phase so that they can be separated. In paper chromatography, different pigments can be separated based on their solubility. A pigment that is more soluble than another will generally travel farther because it’ll be easier for it to dissolve in the mobile phase and be carried with it along the paper.
Extra: A more accurate way to identify colored components in a solution using paper chromatography is by determining their retention factor (Rf value). The Rf value is the ratio between how far the component travels and the distance the mobile phase (solvent) travels from a common starting point (the line you drew on the strips). If other conditions are kept the same, the Rf value for a certain component should be consistent. You can do this activity again but this time measure these distances and calculate the Rf value for each component. Based on the Rf values, can you identify which dyes are used in the different colored M&M candies by comparing them to the known food coloring dyes?
Extra: In this activity you used M&M candies, but you could try it with other colored candies as well, such as Skittles. Does the red in Skittles look the same as the red in M&Ms when you test both using paper chromatography? What about their other colors?
Extra: You could try this activity again but this time compare using different kinds of mobile phases (e.g., salt water, water, vegetable oil, isopropyl rubbing alcohol, etc.). Does a dye travel different distances depending on the mobile phase you use? What do you think this tells you about the solubility of that dye in the different mobile phases?
Observations and Results
Did you find that green and brown M&Ms are made up of two dyes, while blue, yellow, and red M&Ms only use one dye? Did some of these dyes match the ones from the red, blue, and green food coloring strips?
You may have seen that blue food coloring has blue and red dyes, red food coloring has two different red dyes, and green food coloring uses a blue and a yellow dye (the yellow may be covered by the blue dye, making it appear green, and all of this can depend on the exact food colorings used). Looking at the ingredients list on the packaging can help you determine exactly which FD&C dyes these are. Blue M&Ms use one of the same blue dyes and red M&Ms share one of these red dyes (you can figure out which by looking at their packaging). If you tried brown M&M’s, you probably saw that they contain a red dye (the same one as red M&M’s) and a blue dye. Green M&M’s also use two dyes, a yellow dye and a blue dye, although the latter may be too faint to easily see. Yellow M&M’s use a yellow dye.
More to Explore
Teisha Rowland, PhD, Science Buddies
Science Buddies |
Chemistry, dyes, food coloring, chromatography, solubility
Explore Our Science Videos
Fire Snake Experiment
Build an Infinity Mirror
Gel Electrophoresis and Forensic Science: Biotechnology Science Fair Project