SCH3U

Name: ______

Date: ______

Paper Chromatography: Separating the Soluble from the Insoluble

Introduction:

Paper chromatography is an analytical technique for separating the components of mixtures based on their solubility. The sample is placed on the chromatography paper (called the stationary phase), and the paper is placed in a chromatography chamber with the chromatography solvent (called themobile phase). The chromatography solvent will move up the chromatography paper bringing certain components of the sample with it. The sample will separate based on the solubility of each component. Components that are less soluble will remain stationary while components that are more soluble will be mobile with the solvent.

Purpose: To separate the ink of different markers using chromatography and use the results to identify an unknown ink.

Materials:

-pencil
-ruler
-tweezers
-3 strips of chromatography paper
-chromatography chamber / -3 chromatography solvents
  • Water
  • Toluene
  • Isopropyl alcohol
/ -3 markers of the same colour
  • Staedtler non-permanent (A)
  • Sharpie (B)
  • Staedtler permanent (C)

Procedure:

  1. Use a pencil to draw a start line about 1 cm from the bottom of the chromatography strip.
  2. Use the 3 markers to make 3 evenly spaced dots on the start line. Label each dot with a pencil.
  3. At the top of the strip, use a pencil to label the solvent “water”.
  4. Pour a few milliliters of water into the chromatography chamber (just enough to cover the bottom).
  5. Use tweezers to carefully lower the chromatography strip into the chamber. Both corners of the strip must enter the solvent simultaneously.
  6. Place the lid on the chromatography chamber.
  7. Allow the solvent to move up the paper.
  8. Use tweezers to remove the chromatography paper once the solvent is ~2cm from the top of the strip. Draw a line across the solvent front.
  9. After the paper is dry, make the appropriate measurements to calculate the Rf value for each ink
  1. Repeat the procedure using toluene and isopropyl alcohol as the solvent.
  2. Obtain the “mystery ink”. Create a procedure to determine the identity of the ink

Observations:

Use the table to record observations and calculate the Rf values.

Solvent / Ink
Staedtler non-permanent
A / Sharpie
B / Staedtler permanent
C
Water
Toluene
Isopropyl Alcohol
Solvent / Mystery Ink

Analysis:

Use the observations to determine the identify of the mystery ink. Discuss any sources of error and improvements.