Sodium benzoate also known as benzoate of soda is the sodium salt of benzoic acid, widely used as a food preservative and a pickling agent. It appears as a white crystalline chemical with the formula C₆H₅COONa. The compound has a molecular weight of about 144.11 g mol^-1 and CAS number 532-32-1. As the benzoate anion it functions as the conjugate base of benzoic acid (pKa of benzoic acid about 4.20), so antimicrobial efficacy is greatest in acidic media where the undissociated acid is present. Sodium benzoate is highly soluble in water as the sodium salt, stable in dry form, and compatible with common excipients and food matrices; it is used in aqueous pharmaceutical formulations, beverages, sauces and brines, and as a microbiological inhibitor in laboratory reagents. Typical analytical characterization includes assay by HPLC or titration, identification by IR and elemental analysis, and residual volatile and benzene screening by GC when applicable.
Parent: Sodium Benzoate
Commercial and pharmacopeial grade sodium benzoate is typically specified to high purity with defined impurity limits to control related substances and reaction byproducts. Typical specification targets used by manufacturers and pharmacopeias include assay generally greater than 99% on a dry basis, loss on drying commonly under 1.0%, and benzoic acid (free acid) limited to about 0.2 to 0.5% depending on the grade. Inorganic anions such as chloride and sulfate are normally controlled to low levels, often below 0.05% each, and heavy metals are limited to low ppm levels, for example not more than 10 ppm for lead expressed as Pb. Related compounds to monitor include benzoic acid and other benzoate salts such as potassium benzoate, traces of benzyl derivatives, and potential benzene formed when benzoates interact with ascorbic acid under certain conditions; benzene and other volatile impurities are typically monitored by GC with specification limits set to meet regulatory thresholds. Routine quality control uses HPLC for impurity profiling and assay, GC for volatile contaminants, and ICP or AAS for elemental impurities.
In medicine sodium benzoate is used primarily as an antimicrobial preservative in topical and some pharmaceutical formulations and as an ammonia scavenger in metabolic disorders; intravenous or oral sodium benzoate is part of treatment regimens for urea cycle disorders and hyperammonemia because it conjugates with glycine to form hippurate which is excreted renally, reducing systemic ammonia levels.
Sodium benzoate is widely used in cosmetic and topical formulations at recommended concentrations and is generally regarded as safe for most people, but it can cause irritation or contact dermatitis in sensitized individuals so formulations are tested for skin compatibility and use concentrations follow cosmetic regulatory guidance.
At regulatory and food additive usage levels sodium benzoate is considered safe for the general population; ingestion or exposure at much higher doses can produce adverse effects, and there are documented concerns about benzene formation in specific beverage formulations containing ascorbic acid so manufacturers control formulation and storage conditions and monitor benzene and other impurities to ensure safety.
