Separating a Mixture of Organic Materials

Forensic Chemistry > 3. Because proteins are a major structural and metabolic component of all living organisms, the analysis of protein samples can be useful in forensic chemistry >
Separating a Mixture of Organic Materials >

Perform a first-hand investigation to carry out chromatography to separate a mixture of organic materials such as the pigments in plants

Paper chromatography

  • performed by placing a small spot of the sample (above the solvent level) at the bottom of a strip of chromatography paper
  • The rate of migration of spot towards the upper part of the paper is dependent on the polarity of the sample being analysed and solvents.

Experiment: Separation of Food Dye by Paper Chromatography

Objective: To separate the organic pigments in “smarties”

Methodology:

  1. Place each smartie into a small beaker. Add drops of water and mix until smarties are dissolved.
  2. Draw a fine line across a strip of filter paper using a capillary tube.
  3. Prepare a 200 mL 1% NaCl solution and pour out into beaker to a depth of about 1 cm
  4. Place the paper strip into the beaker, ensuring the level of liquid is below the line on the paper and that the paper does not touch the sides of the beaker.
  5. Repeat using solvents: distilled water, methylated spirits, kerosene

Results:

  • The chromatograms showed no movement of dye (spot) under the non-polar solvents, kerosene and methylated spirits.
  • The chromatograms in distilled water and NaCl solution (polar solvents) showed separation of the blue colour in both dyes in short period of time

Conclusion:

  • Dyes have found to be water soluble due to better separation in the presence of polar solvents
  • The aforementioned polar solvents are good solvent for the experiment.