How the sun protection factor (SPF) of sunscreen films change during solar irradiation

Binks, Bernard P.; Fletcher, Paul D.I.; Johnson, Andrew J.; Marinopoulos, Ioannis; Crowther, Jonathan; Thompson, Michael A.

Abstract

We have investigated how the sun protection factor (SPF) of different types of sunscreen film varies with “standard” solar irradiation due to photochemical processes. We have used a combination of chemical actinometry, measurement and modelling to estimate the overall quantum yields for the photoprocesses occurring for avobenzone (AVB) and isopentyl p-methoxycinnamate (MC) in either propane-1,2-diol (PG) or squalane (SQ) as solvent. Using the obtained parameters, we have developed models to calculate the evolution of the film spectra and derived SPF values for both non-scattering sunscreen films consisting of solutions of multiple UV filters and for highly scattering Pickering emulsion based sunscreen films. Model calculations for all films are in excellent agreement with film spectra measured as a function of irradiation time using different laboratory light sources. Finally, using the estimated parameters and experimentally validated models, we are able to quantitatively predict how the in vitro SPF values for different film types containing any set combination of UV filter concentrations will vary with time due to photochemical processes induced by irradiation with “standard” sunlight. This provides a useful tool for the rational design and optimisation of new sunscreen formulations.

Citation

Binks, B. P., Fletcher, P. D., Johnson, A. J., Marinopoulos, I., Crowther, J., & Thompson, M. A. (2017). How the sun protection factor (SPF) of sunscreen films change during solar irradiation. Journal of Photochemistry and Photobiology A: Chemistry, 333, 186-199. https://doi.org/10.1016/j.jphotochem.2016.10.027

• Journal Article Type: Article
• Acceptance Date: Oct 20, 2016
• Online Publication Date: Oct 25, 2016
• Publication Date: Jan 15, 2017
• Deposit Date: Oct 25, 2016
• Publicly Available Date: Oct 25, 2016
• Journal: Journal of photochemistry and photobiology A : chemistry
• Print ISSN: 1010-6030
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 333
• Pages: 186-199
• DOI: https://doi.org/10.1016/j.jphotochem.2016.10.027
• Keywords: Sunscreen; Sun protection factor; Photochemistry; Emulsions; Avobenzone; p-methoxycinnamate
• Public URL: https://hull-repository.worktribe.com/output/444554
• Publisher URL: http://www.sciencedirect.com/science/article/pii/S1010603016307468
• Additional Information: This article is maintained by: Elsevier; Article Title: How the sun protection factor (SPF) of sunscreen films change during solar irradiation; Journal Title: Journal of Photochemistry and Photobiology A: Chemistry; CrossRef DOI link to publisher maintained version: http://dx.doi.org/10.1016/j.jphotochem.2016.10.027; Content Type: article; Copyright: © 2016 Elsevier B.V. All rights reserved.
• Contract Date: Oct 25, 2016