Candy Chromatography

Paper chromatography is used to separate the dye mixture from colored candy coatings and compare the separated spots to known food colorings. Measure and compare Rf values to infer which approved food dyes are present.

1. Gather materials: chromatography paper or paper towel, pencil, ruler, scissors, small beakers or cups, pipette or droppers, wooden splints or toothpicks, plate or plastic lid, table salt, water, binder clips, stir stick, assorted colored candies, red/green/blue food coloring.
2. Cut paper into strips about 2 cm by 7–8 cm. With pencil, draw a light baseline 1 cm from one short edge and label each strip with the sample name.
3. Place a single drop of water on a clean plate. Set one candy in the drop for about 3 minutes to dissolve a concentrated puddle of dye. Remove the candy.
4. Use a pipette tip or wooden splint to transfer a tiny amount of the dye to the center of the baseline on a labeled strip. Let it dry. Repeat tiny applications 3–5 times to build a small, dark spot without making a large circle.
5. Prepare replicate strips for the same candy color and repeat with at least two other candy colors.
6. Spot separate, labeled strips with known food colorings (red, green, blue) using the same baseline procedure.
7. Make a 0.1% salt solution by dissolving about 1 g salt in 1 L water (about 1/8 tsp in 4 cups). Pour a shallow layer into a clean beaker or cup.
8. Clip two strips to a wooden splint so they hang side by side without touching. Adjust the liquid level so the strip bottoms just touch the solvent, with the dye spots above the liquid.
9. Allow the solvent to wick upward by capillary action until it is about 0.5 cm from the top edge. Remove the strips.
10. Immediately mark the solvent front with pencil. Let strips dry flat.
11. Measure the distance from the baseline to the center of each separated dye spot and the distance from the baseline to the solvent front. Calculate Rf = (distance traveled by dye) / (distance traveled by solvent).
12. Repeat runs until all candy and food coloring strips have been developed. Record replicate Rf values and compute averages for each colored component.
13. Compare component colors and Rf values from candies to those from the known food colorings to infer matches.

Hands-On Science! e08 — CANDY CHROMATOGRAPHY! - Science North:

Candy Chromatography - Arizona Science Center:

📄 Candy Chromatography: What Makes Those Colors? - Science Buddies: https://www.sciencebuddies.org/science-fair-projects/project-ideas/FoodSci_p006/cooking-food-science/candy-chromatography

• Test a wider variety of candies to see if the “same” color uses the same dye blend across brands.
• Compare different solvents such as water, isopropyl rubbing alcohol diluted with water, or sugar solutions to see how solubility and polarity affect movement.
• Try different papers (chromatography paper, high-quality paper towels, coffee filters) and evaluate separation quality and reproducibility.

• Do not eat candies, dyes, or solvents once used for the experiment; keep food and lab items separate.
• Wear safety glasses when cutting strips and handling liquids; avoid splashes.
• Wash hands after handling dyes and solvents; clean the workspace promptly.
• Use only small amounts of isopropyl alcohol if testing alternate solvents; keep away from flames and ensure good ventilation.
• Check for potential dye or candy ingredient allergies; avoid skin contact with concentrated dyes.
• Dispose of used solutions and paper in the trash; do not pour concentrated dye down sinks without dilution.

• Why do some dye components travel farther than others on the same strip? (They differ in solubility in the mobile phase and in how strongly they interact with the stationary phase, so their relative attractions cause different travel speeds.)
• What does a larger Rf value tell you about a dye component in this setup? (It is more mobile under these conditions, typically more soluble in the solvent and/or less strongly retained by the paper.)
• How can you use known food coloring results to identify the dyes in a candy? (Match both spot color and Rf under the same solvent, paper, and temperature conditions.)
• What would happen if the baseline were submerged in the solvent at the start? (The sample would dissolve directly into the solvent pool, causing streaking or loss of sample and poor separation.)
• Why is it important to keep conditions the same when comparing Rf values? (Rf depends on solvent, paper, temperature, and pH; changing them changes dye–phase interactions and invalidates comparisons.)
• If two different brands show similar Rf patterns but slightly different values, how could you decide whether they use the same dyes? (Run side-by-side on the same sheet, use replicate averages, and compare both color and relative ordering of spots.)