Chromatography Mini Lab: Chem. Hons.
Name:______________________Per:______
Background Information
Chromatography is a method of separation of a mixture that is often used by biochemists,
who study the chemistry of living systems. Chromatography is the general name applied
to a series of methods that employ a system with two phases, (states) of matter: a mobile
phase and a stationary phase. The stationary phase is a solid, and the mobile phase is
either a liquid or a gas. The separation process occurs because the components of mixture
have different affinities for the two phases and thus move through the system at different
rates. A component with a high affinity for the mobile phase moves quickly through the
chromatographic system, whereas one with high affinity for the solid phase moves more
slowly. This can be explained well by the following example:
One simple type of chromatography, paper chromatography, employs a strip of porous
paper, such as filter paper, for the stationary phase. A drop of the mixture to be separated
is placed on the paper, which is then dipped into a liquid (the mobile phase) that travels
up the paper as though it were a wick.
The compound can be identified by their Rf values, which is defined as the ratio of the
distance traveled by the spot and the distance traveled by solvent (solvent front).
Rf= distance traveled by the compound (spot)/ distance traveled by the solvent (solvent
front)
2/16/2016
Chromatography Lab: ChemIsTry Honors
1
Different compounds can be identified by their Rf values which is standard for a given
compound. In this lab, we will use both color of spot and Rf values to detect different
compounds.
Prelab
1. What is chromatography?
__________________________________________________________________
__________________________________________________________________
2. How does chromatography work?
__________________________________________________________________
__________________________________________________________________
3. How many phases are there in this process?
__________________________________________________________________
4. If a solute has more affinity for solid phase, then will it move faster or slower?
__________________________________________________________________
5. What is the stationary phase in paper chromatography?
__________________________________________________________________
Purpose (These questions are there so you can get a better understanding of the
purpose of lab. You don’t have to answer them)
1. What is the origin of the colors of the ink in the pens? Is the ink made up of
several dyes or just one?
2. Does the manufacturer use the same dyes for different color inks? If so, they will
be the same color and move the same distance relative to the water (same RF).
3. Finally, what happens if the water is altered by adding something like table salt
(sodium chloride) to it? Does this cause any changes in the movements of the
dyes or effectiveness of the separation method?
Materials
Per lab Group ( for groups of four)








Strips of filter paper-8
100ml Beakers-4
4 Different colored markers
4 Stirring Rods
Pencil-1
Ruler-1
DI water bottle
Salt Water
2/16/2016
Chromatography Lab: ChemIsTry Honors
2
Procedure
Preparing Paper:
1.Use pencil to draw line about 1 cm from one end.
2. Place a small spot of ink on the pencil line. (the smaller the dot the better)
3. Fold the paper about 1 cm from the end of the filter paper.(the opposite end from
where the dot was placed)
4. Write the name of the color just under the folded end.
5. Pour distilled water into the beaker until it is deep enough to just touch the filter paper.
(be sure the water will not touch the ink spot)
6. Hang the filter paper over a stirring rod so it just reaches the water. (make sure the
paper does not stick to the sides of the beaker).
7. Repeat this procedure for the other three colors.
Performing the chromatography:
1. Allow the water to rise on the papers until it is about 1 cm from the top.
2. Remove the paper
3. Mark the solvent front (how far the solvent traveled)
4. Allow the paper to air dry on your desk.
Using Salt water:
1. Repeat all of the previous steps but instead of using distilled water use salt water.
Interpreting the results: Each person in lab group will interpret results for one color in
both distilled water and in salt water.
1. Once the filter paper has dried, circle each individual color
2. Find the midpoint of each color (each circle) and make a small dot there.
3. Draw a line from this midpoint to the bottom line where the initial color dot was
placed.
Rf = (distance traveled by the compound from the pencil line to the midpoint of the spot)/
distance traveled by the solvent (solvent front).
Data:
1. Stick both the dried chromatograms in this section.
2. Calculate Rf values for each of the chromatograms.
2/16/2016
Chromatography Lab: ChemIsTry Honors
3
Conclusion
1. Which is the stationary phase in this experiment? Which is the mobil phase?
__________________________________________________________________
2. Do the colors in the pens contain one dye or more ? How can you tell that?
__________________________________________________________________
3. Are some dyes found in more than one colors? If yes, then which dye is used in
most colors?
__________________________________________________________________
4. Did changing the solvent affect the way mixture separated?
__________________________________________________________________
5. Using the experimental observation, briefly describe how the color of dyes used
in ink determines the color of that ink?
__________________________________________________________________
__________________________________________________________________
Extension: Run chromatograms for red, blue, green and yellow food coloring and also
for one color of your favorite candy plain water. Coffee filter works best, but if you don’t
have one, then you may use a paper towel.
 Compare the spots (how many spots, of what color etc.) obtained by food coloring
and candy.
 Calculate Rf values for any ONE food coloring.
 Comment on the similarities and differences of the compounds in your candy and
the other food colors.
 Stick the chromatograms to this sheet
2/16/2016
Chromatography Lab: ChemIsTry Honors
4