Reviewing Modified Vitamin C Serum Formula Stability

Subject: Review of Vitamin C Serum Formula

Thank you for sharing your adapted Vitamin C serum formula and process. You've provided a detailed breakdown of the ingredients and steps, aiming for a clear serum based on the Skinceuticals C E Ferulic kit.

We have reviewed your formula and the staff's feedback. The staff noted that they cannot guarantee the stability of this modified formula compared to the original, which has undergone extensive testing.

They raised two specific points:

• Ferulic Acid Solubility: The staff is unsure if 0.5% Ferulic Acid will completely dissolve in 3% 1,2-Hexanediol. They recommend performing a test to confirm this solubility.
• Removal of Ethoxydiglycol: The original Skinceuticals formula likely included Ethoxydiglycol. The staff expressed concern about its removal, as Ethoxydiglycol is often used to enhance the penetration of ingredients like Vitamin C into the skin and may also contribute to the stability of Vitamin C. Removing it could potentially affect both the efficacy and stability of your serum.

L-Ascorbic Acid (Vitamin C) is known to be unstable and prone to oxidation, especially in water-based formulations. The stability of a Vitamin C serum is critical for its effectiveness. Modifications to a proven formula, such as changing solvents or removing ingredients like Ethoxydiglycol, can significantly impact this stability.

Therefore, while your formulation process seems logical based on the solubility properties of the ingredients (e.g., dissolving Ferulic Acid in 1,2-Hexanediol and adding it later), it is highly recommended to perform stability testing on the final product. This would involve observing the serum over time for changes in color, clarity, odor, and pH, particularly under different temperature conditions (e.g., room temperature and elevated temperature for accelerated testing).

In summary, the staff's feedback highlights potential challenges regarding Ferulic Acid solubility and, more critically, the potential impact on Vitamin C stability due to the removal of Ethoxydiglycol. Testing the Ferulic Acid solubility and conducting comprehensive stability tests on your final serum are crucial steps to ensure its effectiveness and shelf life.