Paper chromatography is a widely used method of separation. The lab will show the basic techniques of paper chromatography. In this lab, the separation of the dyes used in two different kinds of candy is performed. The candy dyes may also be compared to solutions of FD&C food dyes. Purpose: The purpose of this experiment is to separate and compare dyes found in two different kinds of candy. Materials:Materials: Candy with a colored coating, like Skittles® or M&Ms® (4 different colors) • Rubbing alcohol or isopropyl alcohol • Coffee filters (2) • Tall glasses or plastic cups (2) • Pencil • Ruler • Tape • Foil or paper plate • Table salt • Water • Toothpicks or cotton swabs (4) • Measuring cups/spoons • Clean pitcher or 2-liter bottle Procedure: 1. Coffee filters usually are round, but it’s easier to compare your results if the paper is rectangular. So your first task is to cut the coffee filter into a rectangle measuring three cm by nine cm.
You will need two of these strips to complete the lab. 2. Space four drops of water (or however many colors you are testing) equally distant on a piece of foil or plate. Position one candy of each color on the drops. Give the color about a minute to come off into the water. Dispose of the candy. 3. Using a pencil (do not use a pen), draw a line one cm (1/2 inch) from the edge of one end of one strip of paper. 4. Make four pencil dots (one for each color of candy you will be examining) along this line, about 0. 5 cm (1/4 inch) apart.
Underneath each dot, label the color of the candy you will test on that spot. You won’t have space to write the whole color name, so try abbreviations like B for blue, G for green, etc. 5. Dip a toothpick or cotton swab into one sample of colored water and dab the color onto the pencil dot for that color. Use a clean toothpick for each color. Try to keep each dot as small as possible. Allow the filter paper to dry, and then go back and add more color to each dot, repeating this step a total of three times for each color. 6.
Prepare the salt solution by mixing 1/8 teaspoon of salt and three cups of water in a clean pitcher or 2-liter bottle. Stir or shake the solution until it is dissolved. This will produce a 1% salt solution. 7. Pour the salt solution into a clean tall glass so that the liquid level is 1/4 inch (0. 5 cm). 8. Tape the strip to a pencil and rest the pencil on top of the jar so that the strip hangs into the jar. The goal is to have the end of the chromatography strip just touching the surface of the solvent solution, with the colored dots above the surface of the liquid.
Make sure that the colored spots do not come in direct contact with the liquid in the bottom of the glass. 9. Capillary action will draw the salt solution up the paper. As it passes through the dots, it will begin to separate the dyes. When the salt water is 1/4 inch (0. 5 cm) from the top edge of the paper, remove it from the glass and place it on a clean, flat surface to dry. 10. Repeat steps two through nine (using the second strip of paper and a clean glass) to test the same four colors using the alcohol instead of the saltwater solution at the bottom of the glass.