2:	Student understanding of chromatography: a hands-on approach using plant pigments.

Authors:	Emry, Randy(A)Curtright, Robert(B)Markwell, John(C)
Affiliations:	(A): Lincoln Southeast High School (B): Lincoln Northeast High School (C): Dept. Biochemistry, Univ. Nebraska
Presenter:	Markwell, John , markwell@unl.edu

We present a collaborative activity which challenges students to develop a chromatographic solvent with the appropriate polarity to separate leaf chlorophyll and anthocyanin pigments by TLC. The suggested activity has been tested with both high school advanced chemistry students and with undergraduate students in an introductory biochemistry class. The exercise includes a demonstration introducing the basic principles of partitioning and differential distribution based on solubility. For the student activity, the materials to be used are leaves of the variegated Coleus plant, plastic backed silica TLC plates, 2-propanol, acetone and methanol. Students may work collaboratively within a set of boundary parameters to optimize the chromatographic solvent through a series of rapid, successive iterations of chromatography. Furthermore, students can use these chromatography systems to carry out independent projects.