Combining Vitamin C Derivatives in Formulations

You're experiencing difficulty dissolving Magnesium Ascorbyl Phosphate (MAP) at 8%, which is understandable as concentrations above 8% can be challenging to dissolve. Reducing the concentration to 5% should help with this issue.

Regarding your question about replacing some MAP with Ethyl Ascorbic Acid and using them together, it is generally not recommended to combine Magnesium Ascorbyl Phosphate and Ethyl Ascorbic Acid in the same formula.

Here's why:

• Magnesium Ascorbyl Phosphate (MAP) is most stable and effective in an alkaline pH range, specifically between pH 7 and 9.
• Ethyl Ascorbic Acid is most stable and effective in a more acidic pH range, between pH 3.5 and 6.0.

Creating a formula that satisfies the optimal pH requirements for both ingredients simultaneously is not feasible. Combining them at a pH that is a compromise between these ranges will likely reduce the stability and efficacy of both Vitamin C derivatives.

While other ingredients in your proposed formula, such as Panthenol (Vitamin B5) and Hyaluronic Acid, are stable across a broader pH range (Panthenol pH 3.5-7.0, Hyaluronic Acid pH 3.0-9.0), the incompatibility of the two Vitamin C forms is the primary concern.

Therefore, instead of using both, it would be better to choose one Vitamin C derivative that best suits your formulation goals and target pH. If you prefer the properties of Ethyl Ascorbic Acid and its solubility, using it alone at an appropriate concentration (e.g., 3% as you proposed, or up to 10%) in a formula adjusted to its optimal pH range (3.5-6.0) would be more stable and effective. If you prefer MAP, use it alone at a concentration that dissolves well (e.g., 5% or up to 8% with careful dissolution) in a formula adjusted to its optimal pH range (7-9).