Stability of Vitamin C (Ethyl Ascorbic Acid) and Collagen in Cream Formulation

Addressing Your Questions on Ethyl Ascorbic Acid, Disodium EDTA, and Collagen

Thank you for your questions regarding your cosmetic formulation.

1. Color Change Without Disodium EDTA: Yes, if you do not include Disodium EDTA in a water-based formula containing Ethyl Ascorbic Acid (a Vitamin C derivative), the cream is highly likely to change color over time, typically turning yellow or brown. Disodium EDTA acts as a chelating agent, binding to metal ions (like copper or iron) that can catalyze the oxidation and degradation of Vitamin C. By sequestering these ions, EDTA helps stabilize the Ethyl Ascorbic Acid, preserving its efficacy and preventing discoloration.

2. Collagen Solubility with Disodium EDTA: It is unusual for Disodium EDTA alone to cause collagen powder to precipitate. However, formulation interactions can be complex. More importantly, as noted in the previous reply you received, topical collagen has a very large molecular size (around 100,000 Daltons) and cannot be absorbed through the skin to provide internal benefits. Its cosmetic use is generally limited to surface effects like hydration or film-forming.

Recommendations:

• For Stability: To prevent discoloration and ensure the stability of your Ethyl Ascorbic Acid, it is strongly recommended to include Disodium EDTA at the suggested concentration (0.2%) in your water phase.
• For Collagen: Given that topical collagen is not absorbed, you may wish to reconsider its inclusion if your goal was absorption-based skin benefits. If you still wish to include it for other reasons and encounter solubility issues with EDTA present, it might be related to the specific collagen type, the order of ingredient addition, or the formula's pH. However, the priority for preventing discoloration is the inclusion of EDTA.

In conclusion, including Disodium EDTA is crucial for stabilizing Ethyl Ascorbic Acid and preventing color change. While the collagen solubility issue is less common, topical collagen's limited absorption means its primary intended benefit might not be achieved.