Summer Research Program for Science Teachers

Marietta Cleckley

Uniondale High School



Using Thin Layer Chromatography to Identify Amino Acids in Solution

Students will work in groups to design and conduct an experiment to identify amino acids present in an unknown solution.  This will be accomplished in three (3) lessons. The first lesson will be an introduction to chromatography and to TLC in particular.  The process will be demonstrated and explained.  The second lesson will be an experimental design session where students will work in teams and use a guided worksheet to design a controlled experiment to identify the unknowns. 

It will take a great deal of time for students to design the experiment.  A more detailed lesson on controlled experiments beforehand will help.  Also, an Experimental Design Worksheet  (attached) helped students to focus on the task.  Each group must submit a design worksheet for the teacher’s approval before they can go on to lesson three.  [Teaching Standard B- Focus and support inquiry while interacting with students] The third lesson will be for students to actually set up and conduct the experiments they have designed. 


Lesson 1 - An Introduction to Chromatography

Objectives: Students will review chromatography and related terms.  They will observe paper and thin layer chromatography and identify the principles of both.


Motivation: Students have already conducted paper chromatography.

          So, ask for a volunteer to explain the principal of chromatography. [9-12 Content Standard B- Structure and properties of matter]

          Use student work to review previous chromatography lessons.


Review the process of chromatography using the motivation above. Define solution, solvent, solute, solubility, and chromatography.  Explain what is meant by the distance the solvent travels. Describe how this process is used in science. [9-12 Content Standard E- Understandings about science and technology] Explain that all substances may not be soluble in water.  Therefore, other solvents are used depending on what solutes are being dissolved. Give Examples: nail polish remover and acetone; chlorophylls and alcohol.


Define- TLC.

Demonstrate the plates and explain the silica gel layer. 

Inform students that amino acids are not colored and cannot be seen.

Ask students how they think we will be able to see the different amino acids as they separate out?          Answer: plates must be sprayed with a ninhydrin solution or observed under an ultraviolet lamp.


Lesson 2 - Experimental Design

Objectives: Students will work in groups of four and use the Experimental Design Worksheet to design a controlled experiment using TLC to identify unknown amino acids in solution.  Students will be given the names of the known amino acids. Design worksheets will be evaluated and critiqued by the teacher.  Correction/adjustments will be made before experiments will be conducted.


Motivation:  Hand out Experimental Design Worksheet.  Ask students to describe a controlled experiment. 

Direct students into teams to design the experiment. 


Collect all design worksheets at the end of the period.


Lesson 3 - Using TLC to Identify Unknown Amino Acids in Solution

Objectives: Students will set up and conduct the experiments they have designed.  They will complete written lab reports including research findings and conclusions. [9-12 Content Standard A- Design and conduct scientific investigations]

Give each group a copy of their Experimental Design Worksheet with comments/corrections/changes.


Direct students to collect materials and conduct their experiment.


Experimental Design Worksheet:


Team Members: _____________________________________








Lab Title: Using TLC to Identify Unknown Amino Acids in Solution.


Objectives: Given solutions of known amino acids and a mixture of unknowns, you must develop lab procedures that will allow you to determine what amino acids are present in the unknown solution.



1. What procedures will you follow?  Be specific and list steps.  You may use references supplied by your teacher.  Use the back of this paper to write your steps if  you need more space.




2. Identify your controls:




3. What materials will you need?


Return to Chemistry Lesson Plans Menu