Overview
ISO 23675:2024 - Cosmetics - Sun protection test methods - In vitro determination of sun protection factor (SPF) specifies an in vitro SPF testing method for sunscreen products. The method uses UV transmittance spectroscopy on UV‑transparent substrates to determine a static sun protection factor (in vitro SPF) across the spectral range 290–400 nm. It applies to emulsions and alcoholic one‑phase formulations, and explicitly excludes loose/compressed powders and sticks. This standard is not intended for assessing water‑resistance.
Keywords: ISO 23675:2024, in vitro SPF, sun protection factor, sunscreen testing, spectrophotometry, solar simulator.
Key Topics and Technical Requirements
- Scope and applicability: Emulsion and alcoholic one‑phase sunscreen formulations; excludes powder/ stick formats and water‑resistance testing.
- Principle: UVR transmittance spectroscopy to derive spectral absorbance and calculate in vitro SPF.
- Measurement range: Spectral modelling between 290 nm and 400 nm with erythemal weighting.
- Materials and reagents: Defined sample substrates (double plate), reference sunscreen, blanks, and ancillary reagents (e.g., white petroleum/glycerin referenced in Annex D).
- Apparatus:
- Spectrophotometers with specified performance and monitoring requirements (see Annex E).
- Solar simulator with defined spectral quality and maintenance requirements (Annex A).
- Automatic positive‑displacement pipette, analytical balance, and robot for applicator spreading (robot specs in Annex F).
- Procedure overview:
- Plate preparation and controlled application of product.
- Measurement of initial absorbance (pre‑irradiation).
- Calculation of the irradiation dose based on pre‑irradiation in vitro SPF, followed by controlled irradiation.
- Post‑irradiation absorbance measurement and final in vitro SPF calculation.
- Validation and reporting: Criteria for pairwise plate results, use of reference sunscreens (Annex C), and required content for the test report.
Practical Applications and Users
- Product formulators and R&D teams: rapid screening of SPF during formulation development.
- Quality control laboratories: routine batch verification and stability testing for static SPF.
- Regulatory and compliance teams: supporting label claims where an accepted in vitro SPF method is permitted.
- Third‑party testing laboratories and certification bodies: reproducible alternative to in vivo SPF testing that reduces time, cost and ethical concerns.
- Manufacturers seeking harmonized, reproducible SPF measurement using spectrophotometry and solar simulators.
Benefits: improved repeatability/reproducibility versus in vivo methods, faster throughput, non‑human model.
Related Standards (if applicable)
- ISO 24444 - Cosmetics - Sun protection test methods - In vivo determination of the sun protection factor (SPF).
- ISO 24443 - Methods for UVA protection / PPD (related erythemal and action spectra references).
- Note: ISO 23675:2024 was prepared by ISO/TC 217 in collaboration with CEN/TC 392.
For implementation, consult the full ISO 23675:2024 text for normative annexes on plate specification, spectrophotometer and robot performance, and reference substances.
