Contact Information

  • Deborah Berkshire Exton
  • Senior Instructor
  • Chemistry
  • University of Oregon
  • Eugene, OR 97403
(541) 346 - 4629

Spectrophotometric Determination of a Food Dye

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This experiment is an adaptation of the classic Beer-Lambert Law experiments, designed for the General Chemistry laboratory course. In this procedure, students prepare stock and standard solutions of the food dye F.D.&C. #40, also known as Allura Red. They then analyze a sample of Kool-AidTM to determine the concentration of Allura Red and the number of glasses necessary to reach the LD-50 value for this substance.

Beer-Lambert Law experiments have classically been performed using aqueous solutions of heavy metals. By substituting a food-dye, this experiment is completely \"down-the-drain\", requiring no waste processing. Additionally, students are taught about chromophores and how the substitution of Allura Red has been implemented to convert the experiment into a green procedure. They are asked to consider how much waste is produced by their class, the risks associated with copper(II) sulfate and how the waste would need to be disposed of if the experiment had been performed with copper(II) sulfate instead of Allura Red.

Summary prepared March 2012 by Dr. Deborah Exton, University of Oregon.


Exton, D. B. General Chemistry in the Laboratory, 2nd edition, McGraw-Hill Learning Solutions, ISBN 0-07-804433-5, Print

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