Experiment ___

Paper Chromatography of Spinach Extract

The purpose of this lab is to use the technique of paper chromatography to separate spinach extract into its two common chemical components-- B-carotene and and Chlorophyll. The chemical B-carotene has a molecular formula of C40H56, while Chlorophyll, a much larger molecule, has a molecular formula of C55H72O5N4Mg.
Paper chromatography operates under the premise that larger, heavier molecules will not be able to defeat the forces of gravity, thus traveling lesser distances up the chromatography paper. Molecules of different sizes and weights can therefore be separated by chromatographic means. Today's lab focuses upon the size difference between chlorophyll and B-carotene through the use of paper chromatography.

MATERIALS

1 - 400 ml beaker
1 - quarter
1 - metric ruler
1 - piece of chromotography paper
1 - spinach leaf
1 - scissors

PROCEDURE

  1. Each group member must obtain the materials listed above.
  2. Using the scissors, cut the chromotography paper into a rectangle.
  3. Measure up 2 cm from the end of the paper and fold, do not write or draw a line!
  4. Along the top side of the crease, lay the spinach leaf atop the paper and roll the quarter on its edge parallel to the crease at the bottom of the paper.
  5. Be sure that the spinach creates a green line across the bottom.
  6. Hang the filter paper from a stirring rod and rest the stirring rod on the top of the first beaker. (do not allow the paper to touch the side of the beaker)
  7. Using the other beaker, carefully add enough petroleum ether to the beaker with the chromatography paper to a point about 1 cm below the spinach line.
  8. The petroleum ether will be absorbed up the paper by capillary action. The water will then transfer the molecules of less molecular weight farther up the paper. Those molecules which are larger will fail to travel as far up the paper.



ANALYSIS QUESTIONS

  1. Given the completed chromatograph, which color band indicates the presence of chlorophyll?
  2. Given the completed chromatograph, which color band indicates the presence of beta carotene?
  3. Based upon their chemical formulas, which molecule is heavier, B-Carotene or Chlorophyll?
  4. Do your results support this?
  5. Attach chromatograph to the space below... after it dries!!!