Sodium Benzoate: Key Information
CAS No.: 532-32-1
Description:
- Sodium Benzoate is the inactive salt of benzoic acid.
- Soluble in water where it converts to benzoic acid at a low pH.
Activity:
- Benzoic acid is pH-dependent.
- Shows some activity up to pH 6 (about 1.55%).
- Most active at pH 3 (94%).
- Considered primarily an anti-fungal, with some activity against bacteria.
- Poor against pseudomonads.
- Inactivated by non-ionics and by raising the pH.
Preservative Use:
- Not a broad-spectrum preservative for cosmetics; should be combined with other preservatives.
- If used, the pH of the finished product may need to be lowered to release the free acid for useful activity.
- Often combined with Potassium Sorbate in low pH products for synergistic preservative effect against yeast and mold.
Applications:
- Commonly used as a preservative in various cosmetic and personal care formulations.
Synergies:
- Combined with Potassium Sorbate to enhance preservative efficacy, especially against yeast and mold.
Note:
- Sodium Benzoate is a widely used food preservative as well.
Additional Recommendations:
- Ensure compatibility with other ingredients in the formulation.
- pH adjustment may be necessary for optimal preservative activity.
Safety:
- Generally regarded as safe for use in cosmetics when used within recommended concentrations.
Reference:
- Always refer to specific formulation guidelines and regulatory standards for the appropriate use and concentration.
Activity of Benzoic Acid at Various pH:
- pH 3: 94% Active Benzoic Acid
- pH 4: 61% Active Benzoic Acid
- pH 5: 13.7% Active Benzoic Acid
- pH 6: 1.55% Active Benzoic Acid
- pH 7: 0% Active Benzoic Acid
Concerns Regarding Sodium Benzoate and L-Ascorbic Acid:
There is a concern that the combination of Sodium Benzoate and L-Ascorbic Acid in cosmetic products may lead to the formation of benzene, a known human carcinogen. The presence of ascorbic acid and benzoates alone does not inherently result in benzene formation. Specific conditions are required for trace levels of benzene to be produced, including heat, ultraviolet light, and metallic ions in the mixture.
Key Points:
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Formation of Benzene: The combination of ascorbic acid and benzoates alone does not lead to benzene formation.
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Additional Conditions: Trace benzene formation requires additional factors such as heat, ultraviolet light, and metallic ions.
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EDTA's Role: The use of EDTA, which chelates metallic ions, can assist in inhibiting benzene formation.
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Citric Acid Interaction: Citric acid is not believed to induce significant benzene production with benzoic acid. However, evidence suggests that in the presence of ascorbic acid and benzoic acid, citric acid may accelerate benzene production.
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Avoidance Recommendation: To minimize the risk of benzene formation, the use of Sodium Benzoate, L-Ascorbic Acid, and Citric Acid in the same cosmetic formulations is advised against.
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Microbial Testing: All cosmetic products should undergo microbial testing to ensure the efficacy of the preservative system.
INCI: Sodium Benzoate
Note: Formulators should be cautious about combining specific ingredients to prevent unintended reactions, and appropriate testing should be conducted to ensure product safety and stability.
Recommended Use percentage: Up to 1%
Solubility: Soluble in water up to 55%.