Formulation Feasibility Analysis

Regarding your proposed formulation:

1. Alpha Arbutin 2%: This concentration is within the recommended usage rate (0.2-2%) and is the recommended level for skin brightening.
2. Double Hyaluron Liquid 2%: This concentration is within the recommended usage rate (1-20%). Double Hyaluron Liquid contains 5% Hyaluronic Acid, so 2% of this liquid provides 0.1% actual Hyaluronic Acid, which contributes to hydration.
3. L-ascorbic acid (Ultra fine) 3%: This concentration is within the recommended usage rate (3-15%) for wrinkle reduction or whitening.
4. Ethoxydiglycol 2%: This concentration is within the current recommended usage limit (not more than 2.6%) for leave-on products.
5. Purified Water: This will serve as the base.

Feasibility and Considerations:

Combining these ingredients is possible in terms of solubility and concentration limits. However, the primary challenge lies in achieving long-term stability, particularly for L-ascorbic acid, due to the pH requirements of the ingredients:

• Alpha Arbutin is most stable at a pH between 3.5 and 6.5.
• L-ascorbic acid requires a pH between 2.0 and 4.0 for effectiveness, and the FDA requires a pH of at least 3.5 for leave-on skin products. The product description also notes that L-ascorbic acid is not stable when dissolved directly in water and recommends using stabilizers like Protec™ OX and Protec™ UV.
• Double Hyaluron Liquid works within a broader pH range of 3-9.

To maximize the stability and effectiveness of both Alpha Arbutin and L-ascorbic acid, the final formulation's pH would ideally need to be carefully adjusted and maintained within the narrow overlapping range of approximately 3.5 to 4.0. Even within this range, L-ascorbic acid in a water-based solution can be prone to oxidation and degradation over time. Therefore, incorporating appropriate stabilizers is highly recommended to help maintain the potency and shelf life of the product.

In summary, while the formulation can be mixed, careful pH adjustment and potentially adding stabilizers are crucial steps to ensure the stability and efficacy of the active ingredients.