Tributyl citrate

• USP–NFTributyl Citrate

TBC; Citroflex 4; butyl citrate; citric acid tributyl ester

Tributyl 2-hydroxypropane-1,2,3-tricarboxylate · [77-94-1]

UNII 827D5B1B6S · PubChem CID 6507

C18H32O7 · 360.44

Plasticiser

Typical concentrations: — · Dosage forms: Solid

Used as a hydrophobic plasticiser for polymers in pharmaceutical film coatings, for example aqueous dispersions of ethylcellulose or methacrylate copolymers, typically at about 10–35% w/w of the polymer. It is also used as a plasticiser in food-contact plastics, chewing gum base and cosmetics.

A clear, colourless or nearly colourless, oily liquid that is practically odourless. It is the tri-n-butyl ester of citric acid.

Density

about 1.04 g/cm³ at 25 °C

Physical state

clear, colourless, practically odourless oily liquid with low volatility

Refractive index

about 1.44–1.45 (n D 20)

Solubility

practically insoluble in water; miscible with ethanol, acetone, propan-2-ol and vegetable oils

Stable under normal conditions. Store in a well-closed container in a cool, dry place.

Incompatible with strong alkalis, which hydrolyse the ester, and with strong oxidising agents.

Prepared by esterifying citric acid with n-butanol in the presence of an acid catalyst, followed by purification.

Used in oral pharmaceutical products and food-contact materials and generally regarded as of low toxicity. It may cause mild skin and eye irritation.

Observe normal precautions for the quantity handled. Eye protection and gloves are recommended.

Permitted by the FDA as an indirect food additive. Included in the FDA Inactive Ingredient Database (oral capsules and tablets) and in non-parenteral medicines licensed in Europe.

Acetyltributyl citrate; acetyltriethyl citrate; triacetin; triethyl citrate.

Being water-insoluble, tributyl citrate does not leach from films as readily as triethyl citrate, but it must be emulsified into aqueous polymer dispersions and given adequate time to partition into the polymer before coating.