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The purpose of this activity is to introduce the principles and terminology of chromatography and demonstrate the separation of the dyes in Sharpie pens with paper chromatography.

Supplies:
5 beakers

5 covers

Distilled H2O

100% isopropanol or 70% isopropanol

50 ml graduated cylinder

Transfer pipettes

5 strips of filter paper

Different colors of Sharpie pens

Pencil

Ruler

Scissors

Tape

Safety glasses

 

Access the Student Journal for Activity 6

Access the Student Presentation for Activity 6

Activity 6 - Paper Chromatography

Preparing the Isopropanol Solutions

 

  1. Using a Sharpie pen, label your beakers as follows:  0%, 20%, 50%, 70%, and 100%.

 

  1. Use the graduated cylinder to measure the 100% isopropanol and distilled H2O for the isopropanol solutions.  The transfer pipettes may be used for adding/removing small amounts.  Prepare the following isopropanol solutions:  0%, 20%, 50%, 70%, and 100%.  The following tables give the exact measurements necessary to make each of the solutions.  The first table is for solutions starting with 100% isopropanol and second table is for solutions starting with 70% isopropanol.  

 

Isopropanol Solutions for 100% Isopropanol

 

0%

20%

50%

70%

100%

Isopropanol     

0 ml

3 ml

7.5 ml

10.5 ml

15 ml

Distilled H2O

15 ml

12 ml

7.5 ml

4.5 ml

0 ml

Total Volume

15 ml

15 ml

15 ml

15 ml

15 ml

 

 

Isopropanol Solutions for 70% Isopropanol

 

0%

20%

35%

50%

70%

Isopropanol     

0 ml

 4.5 ml

7.5 ml

10.5 ml

15 ml

Distilled H2O

15 ml

10.5 ml

7.5 ml

4.5 ml

0 ml

Total Volume

15 ml

15 ml

15 ml

15 ml

15 ml

 

3.   Pour each of these solutions into their labeled beakers as you make them and cover them immediately to prevent the isopropanol from evaporating. 

 

Prepare the Chromatography Strips

4.   Cut the filter paper into 5 strips that are 5 cm x 8 cm. 

5.   Using the pencil and the ruler, lightly draw a horizontal line 1 cm above the bottom edge of each strip. 

6.   Label the strip on the top right-hand corner with the number to the corresponding solution that it will be placed in. 

7.   Carefully spot each Sharpie pen on the starting line.  For the best results, gently touch the tip of the pen to the paper, let it dry and spot it again on top of the first spot a few time.  Keep the spots small and space them out as much as possible so that the colors will not run together as they separate.

 

Developing the Chromatograms

8.   Remove the covers and place the strips in the beakers.  Make sure the solution does not come above the starting line.  If you need to, remove some of the solution.   

9.   Start keeping time now for your observations.

10. Cover the beakers and let the strips develop until the ascending solution is about 2 cm from the top of the strip.  Watch the solution moving up the strip (not just the colors’ movement).  The colors will not move in some of the solutions.  The strips in low concentrations will finish first.

11. Remove the strips as they finish and let them dry on a paper towel. 

12. Dispose of the isopropanol solutions down the drain with water.

13. Observe the results of the chromatograms.

 

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