Determination of crude in vitro UVA PF

The determination of the crude in vitro UVA protection factor (PF UVA) measures the UVA protection factor of a sunscreen product under laboratory conditions. Long-wave UVA rays penetrate deeply into the skin and are responsible for premature skin aging as well as long-term harmful effects. Accurately evaluating a sunscreen product's ability to filter this radiation is therefore a key step in the development and marketing of photoprotective cosmetics.

What is the UVA protection factor?
Ultraviolet radiation is divided into UVB, primarily responsible for sunburn, and UVA, which penetrate deeper and more insidiously. While the SPF (Sun Protection Factor) mainly characterizes protection against UVB rays, the UVA protection factor specifically measures a product's effectiveness against UVA rays. European regulations recommend a minimum ratio between UVA protection and SPF, making this measurement essential to support a sunscreen product's claims and guarantee balanced protection. The "raw UVA protection factor" corresponds to the measured value before adjustment, a step prior to calculating the final UVA protection factor.

How is the analysis performed?
The analysis is carried out according to the international standard ISO 24443, the reference method for the in vitro determination of UVA protection in sunscreens. The product is applied in a controlled manner to a PMMA (polymethyl methacrylate) plate that replicates the roughness of skin, and then the film's absorbance is measured spectrophotometrically across the entire UV spectrum. The calculation incorporates a controlled irradiation step to account for the photostability of the filters. This in vitro approach has the advantage of being rapid, reproducible, and does not require human volunteers, unlike in vivo methods.

Why perform this test?
For manufacturers of sunscreens and cosmetics, determining the UVA protection factor (PF UVA) addresses several needs: supporting and validating protection claims on packaging, verifying compliance with European regulatory recommendations (UVA/SPF ratio), comparing the effectiveness of different formulations during development, and monitoring batch-to-batch protection consistency. Having a reliable and standardized value strengthens product credibility and facilitates market access.

Related Analyses
For a complete characterization of photoprotection, this analysis is complemented by other services from our catalog: the determination of the in vitro SPF, which assesses protection against UVB rays, and the determination of the critical wavelength, an indicator of the spectral range of protection (the criterion of "broad spectrum"). These three measurements, often performed together, provide a comprehensive view of the effectiveness of a sunscreen product. This service falls under the cosmetics.

Why choose YesWeLab?
At YesWeLab, we collaborate with a rigorously selected network of laboratories, most of which are certified and/or accredited (ISO 17025, COFRAC). These laboratories are chosen based on your specific needs, the matrices to be analyzed, and the required analytical techniques or methods. If you have any particular requirements, please do not hesitate to specify them in your request: our scientific team will do everything possible to respond accurately and promptly. Since 2020, numerous manufacturers, distributors, and engineering firms have entrusted us with the management of their analyses, sending us their samples through our digital platform. To learn more or submit a specific request, contact our team today.