Paper Chromatography Lab Report Paper (Page 2 of 4) in pdf

Paper Chromatography Lab

7. If the ink you are testing does not spread out, re-test it using pure rubbing alcohol. (This

means that the ink is not water soluble)

8. When the solvent reaches the top, quickly remove the strip(s) of paper and mark WITH

PENCIL the solvent front and the position of each color dye. (If your dye is a pure substance,

you may have only one color spot to mark. If it is a mixture of several dyes, you will have

multiple pigment fronts.)

9. Let the strip (s) dry and staple or tape this into your lab report. Label this as the test strip.

Using a cm ruler, measure and record the Rf factor for each color spot on the chromatography

paper. Show the math involved for each calculation.

Part 2-Making a match. (A qualitative test)

1. Obtain from your teacher samples of ink from the two suspects pens. Two suspects have been

apprehended and they each had in their possession a notebook with paper similar to the

ransom note and black pens.

2. Again cut and shape the 2 strips of chromatography paper so that it will fit your container.

3. Mark in pencil a line 1.5 to 2.0 cm above the tip of the paper and place a dot of ink from each

of the suspect’s pen on the pencil line. Then place the strips from the suspect’s pen and the

sample from the ransom note into the container so that the ink spots are just above, but not

touching the solvent.

4. Allow the solvent to travel up the papers. Again when the solvent reaches the top, remove the

paper and quickly mark in pencil the solvent front and the position of the pigment(s). Record the

colors of ink seen from each suspect’s pen. (You do not have to calculate the Fro factors for the

pen).

5. Using the sample obtained from the ransom note, compare the suspects pens to the Ink found

in the ransom note.

Can you make a match between the ransom note and the suspects? Does each pen contain the

same dyes?

What’s Happening

Because molecules in ink and other mixtures have different characteristics (such as size,

charge, and solubility), they travel at different speeds when pulled along a piece of paper by a

solvent (in this case, water or alcohol). For example, many black inks contain several colors.

When the water flows through a word written in black, the molecules of each one of the colors

responds differently to the mobile phase (solvent) and the stationary phase (paper), allowing the

component parts to separate.

Many common inks are water soluble and spread apart into the component dyes using water

as a solvent. If the ink you are testing does not spread out using water, it may be “permanent”

ink. In such cases, you will have to use a different solvent such as rubbing alcohol.

Paper Chromatography Lab Report Paper Page 2