pH Stability Range for Tinosorb S (BEMT) Sunscreen
Asked by: elmer.jr.gacer
On: December 23, 2025
Product Type:
Cosmetics
Question
I would like to know the pH stability range for BEMT (Bis-Ethylhexyloxyphenol Methoxyphenyl Triazine), also known as Tinosorb S.
Specifically, I have the following questions:
- What is the effective pH range for this ingredient within a formulation?
- Are there any specific considerations regarding its stability or its compatibility with other sunscreen filters (both physical and organic)?
- What are the requirements for its solubility in a formula?
Answer
BEMT (Bis-Ethylhexyloxyphenol Methoxyphenyl Triazine), commonly known by the trade name Tinosorb S, is a highly stable organic sunscreen.
pH Stability Range
BEMT is chemically very stable and can be used in a wide pH range, typically from pH 3.0 to 12.0.
Key Characteristics:
- High Photostability: Unlike some other organic filters (like Avobenzone), BEMT does not degrade significantly when exposed to sunlight.
- Broad Spectrum Protection: It provides effective coverage against both UVA and UVB rays (290-370 nm).
- Compatibility: It is compatible with both physical sunscreens (Zinc Oxide, Titanium Dioxide) and other organic filters (like OMC or DHHB).
- Solubility: It is oil-soluble and must be dissolved in a suitable solvent (such as Octisalate, OMC, or LipidSoft) before being added to the formulation.
For optimal formulation stability, it is recommended to maintain the final product's pH within the range suitable for other ingredients in the formula (e.g., if using Zinc Oxide, a pH of 7.0-8.5 is often preferred).
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