Lab 2 Activities

Chromatography

Overview

In this lab activity, you will use paper chromatography to determine if the food colorings used in colored candy the same as the the FD&C approved chemicals.

Materials

Each lab group will need the following materials:

• 25 cm square piece of chromatography paper
• 4 standard dyes (red, yellow, green, and blue)
• 1 piece of candy (random color)
• ethanol
• mobile phase solution
• 1 flask
• 1 large beaker
• 5 applicator sticks
• pencil
• ruler
• stapler

Procedure

1. Obtain a 25 cm square piece of chromatography paper that will fit into the beaker that will serve as the chromatography chamber.
2. Draw a pencil line across the lower end of the chromatography paper about 2 cm from the bottom.
3. Draw additional vertical tick marks along this line every 2 cm
4. Place colored candy in a flask with 2 ml ethanol until the color dissolves into the solution
5. Using an applicator, create a very small spot on a tick mark and allow it to dry.
6. Repeat application on the spot to make a very small and dark spot.
7. Continue to spot reference standards along other tick marks. These reference standards are food coloring.

8. Place approximately 1 cm of mobile phase solution (a very polar salt water solution) into the beaker.
9. Roll the filter paper into a cylinder and fix with staples.

10. Place the cylinder into the beaker and cover for 20 minutes or until the mobile phase reaches 2 cm from the top of the paper.

11. Use the pencil to mark the final distance of the mobile phase and allow the paper to dry.
12. Once dry, measure the distance of each colored spot from the starting point.
    • Each colored spot is a separate analyte.
    • Some samples separate into multiple analytes.
    • Measure EACH one
13. Measure the distance from the starting point to the final point that the solvent reached.
14. Calculate R_f values and tabulate results.

Data tables can be found on the next page.

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