Summer Research Program for Science Teachers
Uniondale High School
2000
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.
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.
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?