How to Separate Food Coloring From Objects Using Chromatography

Chromatography is a laboratory procedure that effectively separates individual components found in a mixture. The process relies on the affinity each component has with respect to a solid material, called the stationary phase, and a solvent, called the mobile phase. You can design a basic chromatographic procedure, called paper chromatography, in order to separate different food colors using common household products. Individual food colors will move, or migrate, through a paper filter as the solvent is absorbed by capillary action. This article will provide you with a basic technique for separating food colors.

Things You'll Need

• Water
• Isopropyl alcohol, 70 percent
• Coffee filters
• Skittles or M&M candies
• Scissors
• Toothpick
• Drinking glass

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Instructions

• 1

  Dissolve the colored surface from Skittles or M&M candy in 1 ml of water. Different colors can be combined to create a mixture of different food dye components to be separated.

• 2

  Cut coffee filter into strips measuring 1 cm by 10 cm. The filter strip will provide the stationary phase for conducting paper chromatography.

• 3

  Place a 2 mm spot of candy colored water on the filter paper strip with the toothpick. The spot should be placed 1.5 to 2 cm above the bottom of the filter paper and be easy to see. If the spot does not appear dark in color, the paper can be spotted again after the initial spot dries to maintain the 2 mm diameter.

• 4

  Pour isopropyl alcohol in the glass with a depth of 1/2 cm. Alcohol is a solvent and provides the mobile phase. The sides of the glass should remain dry. Excess isopropyl alcohol on the sides of the glass could absorb into the filter paper during the test.

• 5

  Place the bottom end of the filter paper into the alcohol. The area spotted with the colored water does not contact the alcohol. The alcohol will slowly move up the filter paper as it is absorbed by capillary action. Placing a cover over the glass could help reduce evaporation of alcohol.

• 6

  Observe the individual colors separate on the filter paper. Dyes with stronger affinity to alcohol will move more quickly than dyes with stronger affinity to the filter paper. Eventually individual colors will become apparent.

• 7

  Remove filter paper when alcohol is 1 cm from the top of the filter paper. The paper should be placed on a flat surface and allowed to dry. The separation of colors can still be observed after the paper is dry.

• 8

  Test and compare candies with different color coatings. Some candy surface color result from more than one food coloring present. Comparing different colors provides an interesting experiment.