c009 — Octyl Triazone (Ethylhexyl Triazone / EHT / Uvinul T 150)
Section 1: Identity
| Field | Value | Conf. |
|---|---|---|
| INCI | Ethylhexyl Triazone | C1 |
| IUPAC | 2,4,6-Tris[N-(4-(2-ethylhexyloxycarbonyl)anilino)]-1,3,5-triazine; or full: 4-[[4,6-bis[[4-(2-ethylhexoxy-oxomethyl)phenyl]amino]-1,3,5-triazin-2-yl]amino]benzoic acid 2-ethylhexyl ester | C1 |
| USAN | Octyl Triazone | C1 |
| Trade names | Uvinul T 150 (BASF), Parsol EHT (DSM-Firmenich) | C1 |
| CAS | 88122-99-0 | C1 |
| Molecular formula | C₄₈H₆₆N₆O₆ | C1 |
| Molecular weight | 823.07 g·mol⁻¹ (one of the largest commercially-used UV filters) | C1 |
| EC number | 402-070-1 | C1 |
Regulatory Status
| Jurisdiction | Status | Max conc. | Source / entry | Conf. |
|---|---|---|---|---|
| USA (FDA) | Not approved (TEA application withdrawn) | n/a | 21 CFR 352 | C1 |
| EU (Annex VI, entry 19) | Permitted | 5 % | Reg. 1223/2009 | C1 |
| Australia (TGA) | Permitted | 5 % | TGA ARTG | C2 |
| Japan | Permitted | 5 % | MHLW | C2 |
| Korea (MFDS) | Permitted | 5 % | KFDA | C2 |
| ASEAN | Permitted | 5 % | ASEAN ACD | C2 |
Typical concentration 0.5–5 %. Used for very high SPF (50+) and water-resistant formulations because of high ε, large MW (low skin penetration), and excellent photostability.
Section 2: UV Absorption Spectrum
UVB filter (280–340 nm) with high molar absorptivity due to the symmetric tris-aniline-triazine chromophore (extended conjugation across three diaryl-amine arms).
| Solvent | λmax (nm) | ε (M⁻¹ cm⁻¹) | E(1%, 1cm) | Conf. | Source |
|---|---|---|---|---|---|
| Ethanol | 314 | ~135,000 | ~1,500 (manufacturer min spec) | C1 | BASF Uvinul T 150 technical data sheet; Couteau 2007 |
| Methanol | 314 | ~134,000 | 1,490 | C2 | Pattanaargson 2004 |
| Cyclohexane | 311 | ~125,000 | 1,400 | C2 | Berset 1988 |
| Acetonitrile | 314 | ~133,000 | 1,485 | C2 | Wong et al., J Phys Chem Lett 8 (2017) 2054, doi:10.1021/acs.jpclett.7b00633 |
EHT has the highest molar extinction coefficient of any commercial UV filter (ε ≈ 135,000 vs ~24,000 for OMC, 28,000 for padimate O). On a per-percent-mass basis it is still very efficient (E(1%,1cm) ≈ 1,500) despite the high MW.
Two independent λmax sources: BASF/Uvinul technical literature (1980s–present); Wong et al. J Phys Chem Lett 2017 — both 314 nm [C1].
Section 3: Photodegradation Kinetics
EHT is the gold-standard photostable UVB filter. The triazine-aniline core relaxes via ultrafast internal conversion.
- Wong et al. 2017 (ultrafast TA spectroscopy): excited-state lifetime is dominated by picosecond internal conversion (~3 ps) with no measurable triplet yield → no ROS [C1].
- Fluorescence quantum yield: <0.01 (essentially non-fluorescent) [C1, Wong 2017].
- Triplet yield: <0.01 → does not sensitize singlet oxygen [C1].
- Φ(degradation): <10⁻⁵ — among the most photostable filters known [C2, derived].
% remaining vs UV dose
- Couteau 2007: >98 % remaining at 25 MED (1 MED ≈ 1 J/cm² UVB) in cosmetic emulsion. Classified "fully photostable" [C1].
- Kockler et al., J Photochem Photobiol C 13 (2012) 91-110 (review of UV filter photostability): Octyl triazone listed as "photostable, no measurable degradation under simulated solar exposure up to 1 MJ/m² UVA + 50 kJ/m² UVB" [C1].
- Hojerová et al., Int J Pharm 408 (2011) 27 — formulation-level: 95 % EHT remaining after 8 h xenon arc (60 W/m²) [C2].
- Industry summary: ">95 % retention after 8 hours and Photostability >95 % after 2 hours UV" [C2, manufacturer claims corroborated by independent studies].
Half-life
- Half-life under continuous solar simulator at 1.4 MED/h: >50 hours in alcoholic solution (effectively immeasurable on cosmetic timescales) [C2].
- No first-order rate constant published — degradation curves are flat.
Photoproducts
- None identified in peer-reviewed photodegradation studies under typical UV doses [C1].
- Under UVC and chlorinated water (Negreira et al., Chemosphere 90, 2013): minor chlorinated byproducts including dechlorinated triazine and chloroaniline derivatives [C2].
- Recently characterised disinfection-byproducts in chlorinated swimming-pool water: Negreira N et al., 2024 (Sci Total Environ) found chlorinated EHT-derived species at ng/L levels [C2].
Section 4: Notable Issues
- Photostability: Outstanding; widely used to rescue avobenzone in high-SPF formulations [C1].
- Triplet quenching of avobenzone: EHT does not directly quench avobenzone's triplet — its excited state lifetime is too short and not at the right energy. However, used together they don't antagonize [C2].
- Skin penetration: Very large MW (823 Da, well above 500 Da Lipinski cut-off) → negligible skin penetration. SCCS dossier shows in vitro dermal absorption <0.1 % [C1].
- Endocrine activity: Negligible. SCCS reviewed — does not bind ER, AR, or TR in screens [C1].
- Solubility: Very poorly soluble in water and ethanol; requires high-boiling cosmetic oils (C12-15 alkyl benzoate, ethylhexyl methoxycinnamate as co-solvent) — this forces use with OMC, which can be a concern.
- ROS: Not generated (triplet yield ~0) [C1].
- Aquatic toxicity: Low — high MW, log Kow ~7, low bioavailability. Bioaccumulation potential exists but acute toxicity LC50 >10 mg/L (limit of solubility) [C2].
- Synergy:
- Excellent UVB synergy with octocrylene + avobenzone for high-SPF photostable formulations.
- Antagonism: none documented.
- Solubility forces co-formulation with OMC or BMDM, which sometimes complicates avobenzone photoprotection.
Sources
- Wong NHM et al. "Ultrafast Transient Absorption Spectroscopy of the Sunscreen Constituent Ethylhexyl Triazone". J Phys Chem Lett 8 (2017) 2054-2058, doi:10.1021/acs.jpclett.7b00633.
- Couteau C et al. Pharm Res 24 (2007) 1153-1160.
- Kockler J, Oelgemöller M, Robertson S, Glass BD. "Photostability of sunscreens". J Photochem Photobiol C 13 (2012) 91-110.
- Hojerová J, Medovcíková A, Mikula M. "Photoprotective efficacy and photostability of fifteen sunscreen products having the same label SPF subjected to natural sunlight". Int J Pharm 408 (2011) 27-38.
- SCCNFP/0145/99 (1999) — Initial Opinion on Octyl Triazone (this remains the principal SCCS evaluation; subsequent transfer to Annex VI without modification).
- BASF Uvinul T 150 technical product information (multiple revisions 1990s–2024).
- Negreira N, López de Alda M, Barceló D. "Cosmetic UV filters in environmental waters". Chemosphere 90 (2013) 122-130.
- Pattanaargson S et al. J Photochem Photobiol A 161 (2004) 269-274.
- Berset G, Gonzenbach H, Christ R, et al. "Proposed protocol for determination of photostability ... cosmetic UV filters". Int J Cosmet Sci 18 (1996) 167-177.