To find out which colored dyes are used in powdered drink mix and in colored marking pens.
- filter paper cut into twenty 6-by-6-inch (15-by-15-cm) squares
- 10 packages of powdered drink mix, each of a different variety
- tap water
- 10 small plates
- 20 glass jars with lids (or substitute plastic wrap)
- rubbing alcohol
- 10 differently colored marking pens
Paper chromatography, which separates a mixture into its component pigments, will be used to analyze the various colored dyes present in ten flavors of drink mix and ten differently colored marking pens.
- Make pencil marks ¾ inch (2 cm) up from the bottom on both lower corners of ten of the cut-out squares. Draw a line connecting the marks.
- Mix a pinch of each variety of powdered drink mix with a drop of water on each of the ten small plates.
- With the dropper place a droplet of a different variety beneath the pencil line of each filter and allow them to dry. Label the names of each flavor in pencil.
- When each paper has dried, staple each into a cylinder shape, with the droplet stain on the outside.
- Fill ten jars about ½ inch (1 em) high with rubbing alcohol.
- Place one paper cylinder into each jar without touching the sides of the jars.
- Cover the jars with lids or plastic wrap.
- Leave each paper cylinder in the alcohol for about 15 to 20 minutes or until the alcohol reaches the top of the paper.
- Remove the paper filters and allow them to dry. You have just made a chromatogram and should be able to see the different colored dyes that make up each of the powdered drink mixes used.
- To experiment with the colored marking pens, repeat steps 1 through 9, making colored marks on the paper filters instead of using the drink mix.
- Were there more pigments in the chromatograms of the drink mixes or the colored marking pens? What colors were visible in each chromatogram?
- What pigments were found most often in the drink mixes? What pigments were found most often in the marking pens?
- Were the lighter-colored drink mixes and marking pens made up of as many pigments as the darker ones?
- Which of the component dyes traveled furthest up the filter paper? Why?
- Were the drink mixes and marking pens of the same color made up of different pigments?