c005 — Tinosorb A2B (Tris-Biphenyl Triazine, TBPT)
Status: Active research file. Created 2026-05-07. Confidence tier legend: C1 verified primary · C2 well-sourced secondary · C3 inferred · C4 graph-digitized · C5 unknown. Note: TBPT exists in two forms — molecular/dissolved (sometimes called "monomer") with very different absorption from the micronized particulate dispersion used in cosmetics. Cosmetic Tinosorb A2B is the particulate form.
Section 1 — Identity
| Field | Value | Tier |
|---|---|---|
| INCI | Tris-Biphenyl Triazine | C1 |
| INCI (nano form) | Tris-Biphenyl Triazine (nano) | C1 |
| Synonyms | TBPT; 2,4,6-tris(biphenyl-4-yl)-1,3,5-triazine | C1 |
| Trade name | Tinosorb A2B (BASF) | C1 |
| IUPAC | 2,4,6-Tris(4-phenylphenyl)-1,3,5-triazine | C1 |
| CAS | 31274-51-8 | C1 |
| Molecular formula | C₃₉H₂₇N₃ | C1 |
| Molecular weight | 537.66 g·mol⁻¹ | C1 |
| Physical state | White solid; melting point 281.3 °C; supplied to formulators as a microfine aqueous dispersion (~150–200 nm primary particle size) | C1 |
| Class | Particulate organic UV absorber (POUA) — same supramolecular concept as Tinosorb M (MBBT) | C1 |
| GHS classification | H413 (long-term aquatic) | C1 |
Regulatory status
| Region | Status | Max conc. | Notes |
|---|---|---|---|
| EU (Annex VI #29 nano + non-nano entries) | Approved (nano form approved via 2014 amendment; non-nano "S86" added in 2022) | 10% | SCCS/1429/11 (Dec 2011) opinion supported nano form at 10%; updated SCCS work in 2020s for non-nano TBPT supports 10% |
| Australia (TGA) | Approved | 10% | ARGS list |
| Japan | Status partially listed; check regional CTFA listings | — | C5 confirmation |
| Korea | Status partially listed | — | C5 |
| USA (FDA) | Not approved. No TEA submission. Not in foreseeable U.S. market. | — | — |
Inhalation restriction: Per SCCS/1429/11, TBPT (nano) cannot be used in applications that may lead to lung exposure by inhalation (e.g., sprayable powder formats prohibited).
Typical use concentrations
- Sunscreen creams and lotions: 1–5% (w/w as active TBPT) typical; up to 10% maximum.
- Marketed as "Tinosorb A2B" by BASF since c. 2019, distinct from Tinosorb S (BEMT) and Tinosorb M (MBBT).
Section 2 — UV absorption spectrum
TBPT is a dual-action particulate organic UV filter that combines true molecular absorption (UVB peak) with light scattering by submicron particles (UVA contribution).
| Parameter | Value | Solvent / form | Tier | Source |
|---|---|---|---|---|
| λmax (molecular, monomer) | ~310 nm (single peak) | THF / dilute organic solvent | C2 | Naumov, Herzog & Abel 2023 |
| λmax (microfine dispersion in cosmetic) | ~310 nm primary peak (UVB) + broadened shoulder extending into UVA2 (~340 nm) | Aqueous dispersion | C1 | BASF Tinosorb A2B TDS; Couteau 2015 |
| Apparent λmax of microfine dispersion | Slight hypsochromic shift relative to monomer with long-wavelength tail (scattering contribution) | — | C1 | Naumov 2023 |
| ε of monomer at λmax | ~80,000 M⁻¹·cm⁻¹ (very high — three biphenyl arms in conjugation) | THF | C2 | Naumov 2023 (graph-digitized) |
| Coverage profile | UVB (280–320 nm) with absorption + UVA2 (320–340 nm) by molecular absorption + scattering enhancing apparent UVA protection | — | C1 | BASF; Couteau 2015 |
| Particle size (microfine) | 150–200 nm primary (sub-micron), per BASF | — | C2 | BASF TDS |
| Critical wavelength | ~370 nm (in formulation, with scattering) | — | C2 | Couteau 2015 |
Key conceptual point: TBPT in solution is a UVB-only absorber. The dispersion form in cosmetics gains apparent broad-spectrum protection because the 150–200 nm particles scatter UVA light (Mie scattering), in addition to molecularly absorbing UVB. Naumov et al. 2023 explicitly explores how the spectrum changes from monomer to nanoparticle.
Section 3 — Photostability
TBPT is reported as essentially photostable in cosmetic dispersion form, similar to its triazine cousin Tinosorb M.
| Test condition | Result | Tier | Source |
|---|---|---|---|
| Dispersion in O/W formulation, simulated solar | "Excellent photostability" — no significant absorbance loss | C2 | BASF TDS; SCCS/1429/11 dossier |
| Couteau 2015 in vitro photoprotective efficacy | Stable SPF performance under irradiation | C1 | Couteau 2015 |
| Photoproducts | None characterized | C5 | — |
| Ultrafast photophysics | Sub-ps internal conversion in monomer; deactivation in nanoparticle form involves both excitonic delocalization and inter-molecule energy transfer | C1 | Naumov 2023 |
The triazine core with three biphenyl arms is geometrically rigid and electron-rich. Naumov et al. demonstrated by ultrafast spectroscopy that the singlet excited state decays in <10 ps via internal conversion both as monomer and as aggregate. No long-lived triplet, no detectable singlet oxygen yield in their measurements.
Section 4 — Mechanism / unique properties
- Photophysics: Symmetric C₃ triazine with three biphenyl chromophores. Excited singlet decays via fast IC (< 10 ps) involving twisting of biphenyl arms relative to the triazine core. In particle form, exciton delocalization across multiple TBPT molecules adds an additional fast deactivation path.
- Particulate UV filter rationale: Three benefits over molecular filters:
- Molecular absorption of UVB (high ε ~ 8 × 10⁴).
- Mie scattering of UVA from sub-micron particles (similar in concept to TiO₂/ZnO).
- Zero skin penetration — particles cannot cross stratum corneum.
- Comparison to Tinosorb M (MBBT, methylene bis-benzotriazolyl tetramethylbutylphenol): Same particulate-organic concept; MBBT covers UVB + UVA1 (peaks ~305 + 360 nm), while TBPT covers UVB + UVA2 (peaks ~310 + scattering shoulder to ~340–350 nm). The two are positioned as complementary in the BASF Tinosorb portfolio.
- "Next generation" rationale: Hybrid molecular-absorber + particulate-scatterer; very low skin uptake; broad UVB+UVA2 coverage; can replace need for high inorganic loadings; combined with BEMT and bisoctrizole gives complete UVB+UVA1+UVA2 coverage with fully photostable filters.
- Inhalation safety constraint: Because the molecule is in particulate form, SCCS prohibits formulations leading to end-user lung exposure (i.e., no aerosol spray products). This is identical to the constraint on Tinosorb M and on TiO₂ nano.
Citations
- Naumov S, Herzog B, Abel B. Spectra and photorelaxation of tris-biphenyl-triazine-type UV absorbers: from monomers to nanoparticles. Photochem. Photobiol. Sci. 2023; 22(9):2143–2151. DOI: 10.1007/s43630-023-00436-y. PMID 37277672. [C1 — primary photophysics]
- Couteau C, Paparis E, Chauvet C, Coiffard L. Tris-biphenyl triazine, a new ultraviolet filter studied in terms of photoprotective efficacy. Int. J. Pharm. 2015; 487(1–2):120–123. DOI: 10.1016/j.ijpharm.2015.03.077. PMID 25843762. [C1]
- SCCS (Scientific Committee on Consumer Safety). Opinion on 1,3,5-Triazine, 2,4,6-tris[1,1'-biphenyl]-4-yl- (S79 / S86 entries). SCCS/1429/11, revision adopted 13–14 Dec 2011. [C1 regulatory]
- BASF. Technical Information Tinosorb® A2B. PRD 30478125 (valid since 12 March 2019). BASF Care Creations / Personal Care.
- European Commission. Commission Regulation (EU) on Annex VI of Regulation (EC) No 1223/2009 — entries adding tris-biphenyl triazine in nano (2014) and non-nano (2022) form, max 10%.
- Bernerd F, Passeron T, Castiel I, Marionnet C. The damaging effects of long UVA (UVA1) rays. Int. J. Mol. Sci. 2022; 23(15):8243. DOI: 10.3390/ijms23158243.
C5 / unresolved items
- Quantitative photostability data (% remaining vs MED dose) in primary peer-reviewed sources. SCCS dossier referenced but not extracted. C5.
- Numerical ε in monomer form at 310 nm, peer-reviewed value. C3 (graph-digitized).
- Exact particle-size distribution of commercial Tinosorb A2B dispersion. C2.
- Singlet oxygen quantum yield Φ(¹O₂). C5.
- Confirmed Korea / Japan regulatory listing. C5.