Sodium ethyl p-hydroxybenzoate
[CAS# 35285-68-8]

Identification

• Classification: Organic raw materials >> Organometallic salt
• Name: Sodium ethyl p-hydroxybenzoate
• Synonyms: Sodium 4-ethoxycarbonylphenoxide; p-Hydroxybenzoic acid ethyl ester sodium salt
• Molecular Formula: C₉H₉NaO₃
• Molecular Weight: 188.8
• CAS Registry Number: 35285-68-8
• EC Number: 252-487-6
• SMILES: CCOC(=O)C1=CC=C(C=C1)[O-].[Na+]

Properties

• Melting point: >115 °C (free ester) (Expl.)
• Boiling point: 297 °C (1013 hPa, free ester ,decomposition) (Expl.)
• Flash point: 121 °C (Expl.)
• Solubility: 1000 g/L (Expl.)

Safety Data

• Hazard Symbols: GHS05;GHS07 Danger
• Risk Statements: H318-H319
• Safety Statements: P264+P265-P280-P305+P351+P338-P305+P354+P338-P317-P337+P317

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Serious eye damage	Eye Dam.	1	H318
Eye irritation	Eye Irrit.	2	H319
Skin irritation	Skin Irrit.	2	H315

Discovery and Applications

Sodium ethyl p-hydroxybenzoate, commonly known as sodium ethylparaben, is the sodium salt of ethyl p-hydroxybenzoate, a member of the paraben family. Parabens are widely used as antimicrobial preservatives in pharmaceuticals, cosmetics, and food products due to their efficacy in preventing the growth of fungi and bacteria. Sodium ethylparaben has the molecular formula C₉H₉NaO₃ and is the water-soluble form of ethylparaben, enhancing its applicability in aqueous solutions and formulations.

The discovery and use of parabens as preservatives date back to the early 20th century, when their antimicrobial properties were first systematically investigated. The introduction of sodium ethylparaben allowed formulators to incorporate this preservative into water-based products more effectively due to its greater solubility compared to its parent compound. The conversion of ethylparaben into its sodium salt involves neutralization with sodium hydroxide, forming a stable white to off-white powder that readily dissolves in water.

In pharmaceuticals, sodium ethylparaben is used as a preservative in liquid dosage forms such as syrups, suspensions, and injectables. Its inclusion prevents microbial contamination during storage and use, thereby ensuring the safety and efficacy of the product over its shelf life. It is particularly effective against a broad spectrum of yeasts and molds, with moderate activity against bacteria. The concentration used in pharmaceutical formulations is typically low, ranging from 0.01% to 0.2%, depending on the specific application and regulatory limitations.

Sodium ethylparaben is also employed in the cosmetic industry, where it serves as a preservative in products such as lotions, creams, shampoos, and conditioners. It helps maintain the microbial integrity of formulations that may be repeatedly exposed to contamination through consumer handling. Its solubility in water and compatibility with a wide range of cosmetic ingredients make it a versatile and commonly used preservative. In many cases, it is used in combination with other parabens, such as methylparaben and propylparaben, to achieve a synergistic antimicrobial effect and broader spectrum of activity.

The use of sodium ethylparaben extends to the food industry, although its usage is generally more restricted compared to methylparaben and propylparaben. In this context, it may serve as a preservative in processed foods, beverages, and food packaging materials, provided that it complies with food safety regulations established by national and international authorities.

Toxicological evaluations of sodium ethylparaben have consistently shown that it has low toxicity, with rapid metabolism and excretion in humans and animals. It is hydrolyzed to p-hydroxybenzoic acid and its conjugates in the body, which are subsequently eliminated. Regulatory bodies such as the European Medicines Agency and the United States Food and Drug Administration have assessed its safety profile and have approved its use within specified concentration limits.

Despite concerns raised in some studies regarding the potential endocrine-disrupting activity of parabens, current scientific consensus and regulatory assessments indicate that sodium ethylparaben is safe for use at approved levels. Ongoing monitoring and research continue to evaluate its safety in consumer products.

From a physicochemical standpoint, sodium ethylparaben is stable under normal conditions of storage and use. It is less prone to precipitation in aqueous media compared to its ester form and remains effective over a wide pH range, typically between pH 4 and 8. However, it may be less stable at extreme pH values or in the presence of strong oxidizing agents.

In terms of formulation, sodium ethylparaben is compatible with a broad variety of excipients, including alcohols, polyols, surfactants, and emulsifying agents. Its use simplifies the preservation of multi-phase systems by ensuring adequate distribution throughout the aqueous phase.

Due to its effectiveness, solubility, and broad regulatory acceptance, sodium ethyl p-hydroxybenzoate remains an important preservative in modern product development across multiple industries. Its well-established antimicrobial activity, combined with a favorable safety profile, continues to support its widespread application.

References

2004. Acids. Directory of Microbicides for the Protection of Materials.
DOI: 10.1007/1-4020-2818-0_31

2018. The Chemical and Products Database, a resource for exposure-relevant data on chemicals in consumer products. Scientific Data, 5, Article number: 180125.
DOI: 10.1038/sdata.2018.125

2006. Combined Inventory of Ingredients Employed in Cosmetic Products (2000) and Revised Inventory (2006).
DOI: 10.5281/zenodo.2624118