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  Home > JCE Print > Journal of Chemical Education > Issues > 2001  > February  >
In the Laboratory
Drug Distribution: A Guided-Inquiry Laboratory Experiment in Coupled Homogeneous and Heterogeneous Equilibria
John Hein and Michael Jeannot
Department of Chemistry, St. Cloud State University, St. Cloud, MN 56301-4498
Cover
February 2001
Vol. 78 No. 2
p. 224
Abstract
A simple and inexpensive experiment for the study of simultaneous homogeneous and heterogeneous equilibria is described using a common antihistamine drug, diphenhydramine. This experiment gives students an opportunity to study the distribution of a drug in a two-phase system by measuring the concentrations of two chemical species and predicting the others by considering charge balance, mass balance, and equilibrium constant expressions. Furthermore, the acid-dissociation constant and aqueous-organic distribution coefficient can be calculated. The experiment is attractive to students because it represents a simplified model for something experienced in everyday life, namely, drug distribution in the human body. Students also gain experience with two very important analytical techniques, gas chromatography and pH measurement with a glass electrode.
Supplement
A list of chemicals and supplies, additional tips for the instructor, and a student handout including detailed experimental procedures and questions for interpreting results are available.
*  Contents JCE2001p0224W.doc (MS Word 98, Mac)
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*  Citation
 Hein, John; Jeannot, Michael. J. Chem. Educ. 2001 78 224.
*  Keywords
 AcidÐBase Chemistry; Chromatography; Drugs / Pharmaceuticals; Equilibrium; Laboratory Instruction; Quantitative Analysis; Separation Science
*  History
 Created:
Last Updated:		 December 22, 2000
August 31, 2005
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