ISO 23675:2024

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.