Monoethanolamine

• USP–NFMonoethanolamine

Ethanolamine; 2-aminoethanol; 2-hydroxyethylamine; β-aminoethyl alcohol; colamine; MEA

2-Aminoethanol · [141-43-5]

UNII 5KV86114PT · PubChem CID 700

C2H7NO · 61.08

pH adjuster, buffering agent

Typical concentrations: — · Dosage forms: Semi-solid

Used mainly as an alkalising agent and buffer, and to form soaps with fatty acids that act as emulsifiers in topical creams and lotions. It is used in parenteral preparations to form salts of acidic drugs, notably ethanolamine oleate, a sclerosing agent for varices. In cosmetics it is used as a pH adjuster in hair products.

A clear, colourless or pale yellow, moderately viscous, hygroscopic liquid with a mild ammoniacal odour. It is a strong base.

Boiling point

≈ 170 °C

Melting point

≈ 10 °C

Density

≈ 1.02 g/cm³ at 20 °C

pKa

≈ 9.5 (25 °C)

Solubility

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

Very hygroscopic and absorbs carbon dioxide from air; it darkens on exposure to air and light. Store in an airtight container, protected from light, in a cool, dry place; nitrogen blanketing may be used.

Reacts with acids, acid chlorides, anhydrides and esters, and with aldehydes and ketones; forms soaps with fatty acids. It is corrosive to copper, aluminium and their alloys and to some rubbers. As a primary amine it can form N-nitrosamines with nitrosating agents and undergo Maillard reactions with reducing sugars.

Produced by reacting ethylene oxide with aqueous ammonia; the mono-, di- and triethanolamines formed are separated by distillation.

The undiluted liquid is corrosive and strongly irritant to skin, eyes and mucous membranes; at the low concentrations used in formulations, after neutralisation, irritation is much less. Skin sensitisation has been reported. Formulations should avoid conditions that favour nitrosamine formation.

Corrosive: wear chemical-resistant gloves, eye protection (face shield) and protective clothing and handle in a well-ventilated area. It is combustible; keep away from sources of ignition.

Described in the USP–NF. Used in parenteral (as ethanolamine oleate) and topical medicinal products and in cosmetics.

Diethanolamine; triethanolamine; meglumine; trometamol.

In emulsions it is usually reacted in situ with a fatty acid such as stearic or oleic acid to form the emulsifying soap; the resulting systems are alkaline and incompatible with acidic ingredients. Control nitrite levels in raw materials to limit nitrosamine risk.