Compendium of the most significant studies with reference to properties, intake, effects.

Poortavasoly H, Montazer M, Harifi T. Aminolysis of polyethylene terephthalate surface along with in situ synthesis and stabilizing ZnO nanoparticles using triethanolamine optimized with response surface methodology. Mater Sci Eng C Mater Biol Appl. 2016 Jan 1;58:495-503. doi: 10.1016/j.msec.2015.08.065.

Abstract. This research concerned the simultaneous polyester surface modification and synthesis of zinc oxide nano-reactors to develop durable photo-bio-active fabric with variable hydrophobicity/hydrophilicity under sunlight.

Kapeluszna E, Kotwica Ł. The Effect of Various Grinding Aids on the Properties of Cement and Its Compatibility with Acrylate-Based Superplasticizer. Materials (Basel). 2022 Jan 14;15(2):614. doi: 10.3390/ma15020614.

Abstract. The influence of grinding aids (pure triethanolamine and ethylene glycol) on the properties of cements, their compatibility with an acrylate-based superplasticizer and the rheological parameters of mortars were investigated.

Fiume MM, Heldreth B, Bergfeld WF, Belsito DV, Hill RA, Klaassen CD, Liebler D, Marks JG Jr, Shank RC, Slaga TJ, Snyder PW, Andersen FA. Safety assessment of triethanolamine and triethanolamine-containing ingredients as used in cosmetics. Int J Toxicol. 2013 May-Jun;32(3 Suppl):59S-83S. doi: 10.1177/1091581813488804.

Abstract. The Cosmetic Ingredient Review Expert Panel assessed the safety of triethanolamine (TEA) and 31 related TEA-containing ingredients as used in cosmetics. The TEA is reported to function as a surfactant or pH adjuster; the related TEA-containing ingredients included in this safety assessment are reported to function as surfactants and hair- or skin-conditioning agents. The exception is TEA-sorbate, which is reported to function as a preservative. The Panel reviewed the available animal and clinical data. Although data were not available for all the ingredients, the panel relied on the information available for TEA in conjunction with previous safety assessments of components of TEA-containing ingredients. These data could be extrapolated to support the safety of all included ingredients. The panel concluded that TEA and related TEA-containing ingredients named in this report are safe as used when formulated to be nonirritating. These ingredients should not be used in cosmetic products in which N-nitroso compounds can be formed.

Lessmann H, Uter W, Schnuch A, Geier J. Skin sensitizing properties of the ethanolamines mono-, di-, and triethanolamine. Data analysis of a multicentre surveillance network (IVDK) and review of the literature. Contact Dermatitis. 2009 May;60(5):243-55. doi: 10.1111/j.1600-0536.2009.01506.x.

Abstract.  Regarding TEA, we analysed patch test data of 85,098 patients who had been tested with TEA 2.5% petrolatum by Information Network of Departments of Dermatology (IVDK) to identify particular exposures possibly associated with an elevated risk of sensitization. Altogether, 323 patients (0.4%) tested positive. 

Zak AK, Razali R, Majid WH, Darroudi M. Synthesis and characterization of a narrow size distribution of zinc oxide nanoparticles. Int J Nanomedicine. 2011;6:1399-403. doi: 10.2147/IJN.S19693.

Abstract. Zinc oxide nanoparticles (ZnO-NPs) were synthesized via a solvothermal method in triethanolamine (TEA) media. TEA was utilized as a polymer agent to terminate the growth of ZnO-NPs. The ZnO-NPs were characterized by a number of techniques, including X-ray diffraction analysis, transition electron microscopy, and field emission electron microscopy. The ZnO-NPs prepared by the solvothermal process at 150°C for 18 hours exhibited a hexagonal (wurtzite) structure, with a crystalline size of 33 ± 2 nm, and particle size of 48 ± 7 nm. The results confirm that TEA is a suitable polymer agent to prepare homogenous ZnO-NPs.

Triethanolamine (2-[bis(2-hydroxyethyl)amino]ethanol) or TEA, is a chemical compound, a triol and a tertiary amine compound derived from ammonia. It belongs to the ethanolamine family to which monoethanolamine (MEA) and diethanolamine (DEA) belong and was introduced to the market in 1920. Ethanolamines as amines react with acids to form soaps or salts and as alcohols can be esterified and are hygroscopic.

The name describes the structure of the molecule:

• "Tri-" indicates "three", so "Triethanolamine" means that there are three ethanol  groups in the molecule.
• "Ethanol" refers to ethyl alcohol, also known as ethanol, which is a common chemical compound. The presence of three ethanol groups indicates that Triethanolamine contains three -OH groups derived from ethanol.
• "Amine" indicates that the molecule contains an amino group (-NH₂) or a derivative of an amine. In Triethanolamine, the amino group is attached to the central carbon of the molecule.

The synthesis process takes place in different steps:

• Ethoxylation: Ethylene oxide reacts with ammonia in the presence of a catalyst, typically an alkali metal hydroxide or alkoxide. This reaction leads to the formation of monoethanolamine (MEA).
• Ethoxylation of MEA: Monoethanolamine is further reacted with additional ethylene oxide to undergo successive ethoxylation reactions. This step is typically carried out in a controlled manner to ensure the desired degree of ethoxylation.
• Neutralization: The resulting mixture, containing various ethoxylated products, is neutralized using an acid or acid gas, such as carbon dioxide or sulfur dioxide. This step converts any excess alkali present into a salt.
• Distillation: The neutralized mixture is subjected to distillation to separate and purify Triethanolamine from other byproducts and unreacted starting materials. Fractional distillation is often employed to obtain the desired purity.
• Purification: The distilled Triethanolamine may undergo further purification steps, such as filtration or recrystallization, to remove any remaining impurities and obtain a purified final product.

It occurs as a colourless liquid.

Cosmetics

Component added as a chemical intermediate for anionic and non-ionic surfactants, softening humectant and emulsifying agent in shampoos, lotions, creams and other cosmetics acting as a pH regulator.

It is a restricted ingredient III/62 as a Relevant Item in the Annexes of the European Cosmetics Regulation 1223/2009.

As an INCI ingredient, it acts as follows:

• Buffering agent. It is an iingredient that can bring an alkaline or acid solution to a certain pH level and prevent it from changing, in practice a pH stabiliser that can effectively resist instability and pH change.
• Fragrance. It plays a decisive and important role in the formulation of cosmetic products as it provides the possibility of enhancing, masking or adding fragrance to the final product, increasing its marketability.  The consumer always expects to find a pleasant or distinctive scent in a cosmetic product.
• Surfactant - Cleansing agent. Cosmetic products used to cleanse the skin utilise the surface-active action that produces a lowering of the surface tension of the stratum corneum, facilitating the removal of dirt and impurities. 
• Surfactant - Emulsifying agent. Emulsions are thermodynamically unstable and are used to soothe or soften the skin and emulsify, so they need a specific, stabilising ingredient. This ingredient forms a film, lowers the surface tension and makes two immiscible liquids miscible. A very important factor affecting the stability of the emulsion is the amount of the emulsifying agent. Emulsifiers have the property of reducing the oil/water or water/oil interfacial tension, improving the stability of the emulsion and also directly influencing the stability, sensory properties and surface tension of sunscreens by modulating the filmometric performance.

Industry

Stabiliser and pH adjuster for the treatment of polyester surface aminolysis.

Other applications

Solvent and reagent. Used in detergents and household cleaning products, textiles, agricultural herbicides, mineral and vegetable oils, paraffin and waxes, pharmaceutical ointments, petroleum extraction, synthetic resins, plasticisers, adhesives and sealants.

Vulcanisation activator for natural and synthetic rubber, activator in the polymerisation of nitrile rubber.

Safety

It is considered a potentially toxic and pro-inflammatory compound (1).

The most relevant studies on this ingredient have been selected with a summary of their contents:

Triethanolamine studies

Appearance	Colorless liquid
Boiling Point	335.4±0.0 °C at 760 mmHg
Melting Point	21°C
Flash Point	185.0±0.0°C
Density	1.2±0.1 g/cm3
Index of Refraction	1.511
Vapour Pressure	0.0±1.6 mmHg at 25°C
Vapour density	5.14
PSA	63.93000
LogP	-1.11
Safety

• Molecular Formula  C₆H₁₅NO₃   (HOCH₂CH₂)₃N
• Molecular Weight     149.19
• Exact Mass   149.105194
• CAS  102-71-6
• UNII    9O3K93S3TK
• EC Number   203-049-8
• DSSTox Substance ID  DTXSID9021392
• IUPAC  2-[bis(2-hydroxyethyl)amino]ethanol
• InChI=1S/C6H15NO3/c8-4-1-7(2-5-9)3-6-10/h8-10H,1-6H2
• InChl Key      GSEJCLTVZPLZKY-UHFFFAOYSA-N
• SMILES   C(CO)N(CCO)CCO
• MDL number  MFCD00002855
• PubChem Substance ID    57653380
• ChEBI  28621
• ICSC    1034
• NSC   36718
• RTECS   KL9275000
• Beilstein   1699263
• NACRES  NA.25   

Synonyms:

• Tris(2-hydroxyethyl)amine, 2,2′,2′′-Nitrilotriethanol
• Trolamine
• Tris(2-hydroxyethyl)amine

References_____________________________________________________________________

(1) Hu X, Zhou R, Li H, Zhao X, Sun Y, Fan Y, Zhang S. Alterations of Gut Microbiome and Serum Metabolome in Coronary Artery Disease Patients Complicated With Non-alcoholic Fatty Liver Disease Are Associated With Adverse Cardiovascular Outcomes. Front Cardiovasc Med. 2022 Jan 3;8:805812. doi: 10.3389/fcvm.2021.805812.