Diethanolamine

• USP–NFDiethanolamine

bis(2-hydroxyethyl)amine; DEA; diethylolamine; 2,2'-dihydroxydiethylamine; diolamine; 2,2'-iminodiethanol

2,2'-Iminobisethanol · [111-42-2]

UNII AZE05TDV2V · PubChem CID 8113

C4H11NO2 · 105.14

pH adjuster, buffering agent

Typical concentrations: — · Dosage forms: Semi-solid

Used as an alkalising and buffering agent, as a neutralising agent for fatty acids and acidic polymers to form emulsifying soaps in topical emulsions, and to form water-soluble diolamine salts of acidic drugs. Its fatty-acid amides (for example cocamide DEA) are used as foam boosters and thickeners in cosmetics. It is generally used at low levels sufficient to adjust pH or neutralise the acid.

A white, deliquescent crystalline solid or a clear, colourless, viscous liquid (it melts near room temperature), with a slight ammoniacal odour.

Melting point

about 28 °C

Boiling point

about 268 °C

pKa

about 8.9 (conjugate acid)

Solubility

miscible with water, ethanol, acetone and glycerol; slightly soluble in ether and benzene

Hygroscopicity

hygroscopic; absorbs water and carbon dioxide from the air

Hygroscopic and sensitive to light and oxygen, which cause discolouration. Store in an airtight container, protected from light, in a cool, dry place; it attacks copper and its alloys.

As a secondary amine it reacts with acids to form salts and with acid chlorides, anhydrides and esters to form amides. With nitrites or other nitrosating agents it forms the carcinogenic N-nitrosodiethanolamine, so it must not be combined with nitrosating materials. Incompatible with strong oxidisers and with copper and iron.

Made by reacting ethylene oxide with ammonia; the resulting mixture of mono-, di- and triethanolamine is separated by distillation.

Irritant to the skin and especially to the eyes at high concentrations. IARC classifies it as possibly carcinogenic to humans (Group 2B), and the main concern in practice is the formation of nitrosamines; its use in cosmetics is restricted in several jurisdictions.

Wear gloves, chemical goggles and protective clothing, and use in a well-ventilated area; the material is corrosive to the eyes.

Included in the FDA Inactive Ingredient Database for a limited number of products. Nitrosamine risk assessments under current FDA and EMA guidance should cover formulations containing it.

Monoethanolamine; triethanolamine; diisopropanolamine; fatty-acid diethanolamides.

Because of the nitrosamine concern, triethanolamine, aminomethyl propanol or inorganic bases are usually preferred in new formulations. If it is used, control nitrite levels in other excipients and water and test the product for N-nitrosodiethanolamine.