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| Home > JCE Print > Journal of Chemical Education > Issues >
1997
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January
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In the Laboratory
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The Spectrophotometric Analysis and Modeling of Sunscreens
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Christina Walters, Allen Keeney, Carl T. Wigal, Cynthia R. Johnston, and Richard D. Cornelius
Lebanon Valley College, Annville, PA 17003
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January 1997
Vol. 74 No. 1
p. 99
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| Abstract |
Sunscreens and their SPF (Sun Protection Factor) values are the focus of this experiment that includes spectrophotometric measurements and molecular modeling. Students suspend weighed amounts of sunscreen lotions graded SPF 4, 6, 8, 15, 30, and 45 in water and dissolve aliquots of the aqueous suspensions in propanol. The expected relationship of absorbance proportional to log10(SPF) applies at 312 nm where a maximum in absorbance occurs for the sunscreen solutions. Results at 330 nm give similar results and are more accessible using spectrometers routinely available in the introductory laboratory. Sunscreens constitute a suitable class of compounds to use for modeling electronic spectra, and using the computer for the active ingredients ethylhexyl para-methoxycinnamate, oxybenzone, 2-ethylhexyl salicylate, and octocrylene found in commercially available formulations typically predicts the absorption maxima within 10 nm. This experiment lets students explore which compounds have the potential to function as sunscreen agents and thereby see the importance of a knowledge of chemistry to the formulation of household items.
See Letter re: this article.
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| More Information |
 Citation |
Walters, Christina; Keeney, Allen; Wigal, Carl T.; Johnston, Cynthia R.; Cornelius, Richard D. J. Chem. Educ. 1997 74 99.
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History |
Created:
Last Updated: |
July 29, 1999
June 23, 2005
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Link to Letter added (April 2004). Link to Letter added (May 2004).Link to Cover added (June 2004).
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1997
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January
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99
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