Why use pencil to mark chromatography paper

Final Report

Exercise 1

CHEM 180 DL1 Chromatography of Food Dyes

There will be a separation of components of ink. This could create an error with the components that are trying to separate. This said, a pen could not be used.

1. What might happen if a student used a pen to mark the baseline on the chromatography paper?

The solution will move to the top and you would not be able to calculate the Rf value that is compared to the distance that a component traveled in the stationary phase reached by the solvent.

2. What would happen if the student did not stop the development before the solvent reached the top of the paper?

The solvent would wash away the dye.

3. What would happen if the solvent level was above that of the dye spots on the paper at the start of the development?

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Photo 1: Chromatogram

Because the solvents used for chromatography are volatile. If it is not marked immediately, there is a possibility that it may evaporate and then you would not be able to draw the solvent.

4. Why is it important to mark the solvent level on the chromatography paper as soon as you remove it f rom the Petri dish?

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Data Table 1: Chromatogram Data

Sample Solvent front (mm)

Blue 1

Blue 2

48

48

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Red 3

Red 40

Yellow 5

Yellow 6

UK

Sample Spot 1 mm

Blue 1

Blue 2

Red 3

Red 40

Yellow 5

Yellow 6

UK

Sample Spot 1 R

Blue 1

Blue 2

Red 3

Red 40

Yellow 5

Yellow 6

48

48

48

48

48

32

0

0

1

2

3

1

f

1.5

0

0

48

24

16

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UK

Sample Spot 2 mm

Blue 1

Blue 2

Red 3

Red 40

Yellow 5

Yellow 6

UK

Sample Spot 2 R

Blue 1

Blue 2

Red 3

Red 40

Yellow 5

Yellow 6

UK

Sample Spot 3 mm

Blue 1

Blue 2

48

40

1

-4

3

10

7

3

f

1.2

48

-12

16

4.8

6.86

16

47

2

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Data Table 2: FD&C Dyes in Sample

Red 3

Red 40

Yellow 5

Yellow 6

UK

Sample Spot 3 R

Blue 1

Blue 2

Red 3

Red 40

Yellow 5

Yellow 6

UK

-6

3

18

8

4

f

1.02

-24

-8

16

2.67

6

12

Sample: FD&C Dyes in Sample

Unknown Sample red 40

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