Sodium benzoate

• BPSodium Benzoate
• JPSodium Benzoate
• Ph. Eur.Sodium Benzoate
• USP–NFSodium Benzoate

Benzoic acid sodium salt; benzoate of soda; natrii benzoas; sobenate; E211

Sodium benzoate · [532-32-1]

UNII OJ245FE5EU · PubChem CID 517055

C7H5NaO2 · 144.11

Antimicrobial preservative

Typical concentrations: 0.02–0.5% oral · Dosage forms: Liquid

Used mainly as an antimicrobial preservative in oral liquids (typically 0.02–0.5%), in cosmetics (0.1–0.5%) and in foods, and in some parenteral products (up to about 0.5%). Its activity is due to the undissociated benzoic acid, so it is effective only in acidic preparations, best below about pH 4.5. It has also been used as a water-soluble tablet lubricant at about 2–5% w/w, and is used therapeutically in urea-cycle disorders.

A white, granular or crystalline, slightly hygroscopic powder, odourless or with a faint odour of benzoin, with an unpleasant sweetish and saline taste.

pKa (benzoic acid)

4.2 at 25 °C

pH

aqueous solutions are slightly alkaline (about pH 8)

Solubility

freely soluble in water; sparingly soluble in ethanol (90%)

Antimicrobial spectrum

mainly bacteriostatic and fungistatic; more active against yeasts and moulds than bacteria

Aqueous solutions are stable and may be sterilised by autoclaving or filtration. Store the solid in a well-closed container in a cool, dry place.

Incompatible with quaternary ammonium compounds, gelatin, ferric salts, calcium salts and salts of heavy metals such as silver, lead and mercury. Preservative activity is reduced by nonionic surfactants and by adsorption onto kaolin, and by any increase in pH. With ascorbic acid, traces of benzene can form, particularly under heat and light.

Prepared by neutralising benzoic acid with sodium hydroxide or sodium carbonate, followed by evaporation or spray-drying.

Benzoate is conjugated with glycine in the liver and excreted as hippuric acid. It is generally well tolerated orally but may cause urticaria, asthma and other hypersensitivity reactions in sensitive people. Benzoates can displace bilirubin from albumin and should be used with care in jaundiced neonates. JECFA has set a group ADI of 0–5 mg/kg body-weight for benzoic acid and its salts.

Observe normal precautions for the quantity handled. The dust may irritate the eyes and respiratory tract; eye protection, gloves and a dust mask are recommended.

GRAS listed. Accepted as a food additive in Europe (E211). Included in the FDA Inactive Ingredient Database (dental, IM and IV injections, oral capsules, solutions and tablets, rectal and topical preparations) and in parenteral and non-parenteral medicines licensed in Europe.

Benzoic acid; potassium benzoate; benzyl alcohol; sorbic acid.

Check the final pH of the formulation: at pH 4 about 60% of the preservative is in the active undissociated form, but at pH 6 less than 2% is, so efficacy falls sharply as pH rises. Because sodium benzoate itself raises pH slightly, the pH should be adjusted after it is added.