We have developed an undergraduate physical chemistry laboratory experiment examining the properties of three compounds that are active ingredients in common sunscreen products: avobenzone (1-(4-tert-butylphenyl)-3-(4-methoxyphenyl)-1,3-propanedione), oxybenzone (2-hydroxy-4-methoxybenzophenone), octyl 4-methoxycinnamate (OMC) (2-ethylhexyl-4-methoxycinnamate). Aqueous solutions of the compounds are exposed to simulated sunlight in a merry-go-round photochemical reactor. Students work through a kinetic analysis of the direct photolysis of each compound using high performance liquid chromatography (HPLC) determination.  Students also use rates of furfuryl alcohol consumption in the irradiated solutions to analyze the quantum yield of singlet oxygen production. Finally, absorbance and fluorescence spectra, along with each compound's molecular structure are evaluated. Students are then asked to correlate which compounds undergo direct photolysis, generate singlet oxygen, or resist photodegradation based on the compounds' molecular and spectroscopic characteristics.

Spectroscopic and photochemical studies of sunscreen active ingredients: An undergraduate physical chemistry experiment

245th National Meeting (2013)

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