How is Column Chromatography Useful?

Peter D'Amico

Eleanor Roosevelt High School, Manhattan

Summer Research Program for Science Teachers

August 2007

Student Learning Outcomes:  

• SWBAT define what column chromatography is and relate how it is used.

• SWBAT isolate spinach pigments from frozen spinach.

Materials:

• Frozen spinach

• chromatography columns

• cotton, sand

• silica gel

• eluent (commercially purchased)

• test tubes

• flasks

• mortar & pistil

• acetone

Procedure/Instructional Plan:

Preparation Phase/Motivation:

Having not been exposed to chromatography columns, students will get a sneak peek to an advanced form of purification techniques.  Secondly, isolating pigments from spinach is new for students.  The process alone is the motivational tool.

            Description of Instructional Procedure:

• Students will assemble their columns: cotton, sand, silica gel. 

• The spinach will be ground in the mortar and pistil with some ethanol until the acetone has enough pigment in it (should be a dark green). 

• A piece of cotton is then placed in the acetone to soak up some of the spinach pigment and it is then placed in the column. 

• Eluent is poured over the cotton and separation occurs. 

• An orange band will appear first. 

• Collect the pigments with test tubes.

Closure Phase:

            Students will clean their benches and dispose of the chemicals in the proper waste bins.

Assessment:

       Students will submit a lab report the following week in order to report their findings.  Some of the questions to be answered: 

• Why did the orange pigment separate first? 

• Did the eluent have anything to do with this phenomena? 

• How can you improve on this experiment? 

• How does chromatography help scientists identify chemicals? 

• How does column chromatography relate to other identification techniques?

New York State Learning Standards:

A: Science as Inquiry- Students should develop the abilities necessary to do and understand scientific inquiry.

B: Students should develop an understanding of investigating the structure and properties of atoms and molecules as well as chemical reactions. 

G1, G2: Science as a human endeavor, Nature of scientific knowledge (respectively).