Comparing Preservatives for Your Serum

You're asking about the difference between using Phenoxyethanol SA (eq. Optiphen Plus) at 1% and Benzethonium Chloride at 0.1% as preservatives in your serum, especially considering you already have 1% Pure-Succinic™ (Succinic Acid, High-Purity) in the formula. You also asked if increasing Pure-Succinic™ to 2% alone would be better.

Let's look at each ingredient:

• Phenoxyethanol SA (eq. Optiphen Plus): This is a broad-spectrum preservative blend containing Phenoxyethanol, Caprylyl Glycol, and Sorbic Acid. It's effective against bacteria, yeast, and mold. A usage rate of 1% is within the recommended range (0.5-1.25%) for closed container products and provides good overall preservation. It works best in a pH range of 2.0-6.0.
• Benzethonium Chloride: This ingredient acts as both a preservative and an antiseptic. It is known for being very effective at killing germs, even at low concentrations. The maximum permitted usage rate in Thailand and the EU is 0.1%, which is the concentration you mentioned. It is water-soluble and generally considered non-irritating.
• Pure-Succinic™ (Succinic Acid, High-Purity): While primarily used for its benefits in reducing acne inflammation and targeting P.Acnes bacteria, Succinic Acid also has some antimicrobial properties and can function as a preservative, with 2% being the recommended rate for this purpose. It works best in a pH range of 3.5-6.5.

Comparison and Recommendation

Both Phenoxyethanol SA (1%) and Benzethonium Chloride (0.1%) are effective preservatives that can help protect your serum from microbial contamination. They offer different spectrums of activity and work well at the concentrations you proposed.

• Phenoxyethanol SA (1%) provides robust, broad-spectrum protection against a wide range of microorganisms (bacteria, yeast, mold), which is essential for product safety and shelf life.
• Benzethonium Chloride (0.1%) is also very effective, particularly against bacteria, and is used at its maximum allowed level in many regions.

Regarding using Pure-Succinic™ (Succinic Acid, High-Purity) alone at 2% for preservation: While increasing Succinic Acid to 2% enhances its preservative capability, especially against P.Acnes, it may not provide sufficient broad-spectrum protection against all potential contaminants (like certain yeasts and molds) compared to dedicated broad-spectrum preservatives like Phenoxyethanol SA or Benzethonium Chloride. Relying solely on Succinic Acid for preservation might leave your formula vulnerable to certain types of microbial growth.

Conclusion:

To ensure comprehensive protection for your serum, it is generally recommended to use a broad-spectrum preservative system. Adding either Phenoxyethanol SA (1%) or Benzethonium Chloride (0.1%) to your formula containing 1% Pure-Succinic™ would provide better overall preservation than increasing Pure-Succinic™ to 2% alone. Both Phenoxyethanol SA and Benzethonium Chloride are suitable options at the concentrations you mentioned, offering reliable preservation alongside the benefits of Succinic Acid.