Ingredient Compatibility and Stability: Minerals, Electrolytes, and Fatty Acids
Asked by: salitpong_k
On: May 07, 2015
Product Type:
Cosmetics
Question
I have some questions regarding ingredient compatibility and stability in cosmetic formulations:
1. Does Sodium EDTA interact with mineral ingredients like Zinc and Magnesium? Is it necessary to include it even if mineral salts are added?
2. Can mineral salts (Zn, Mg, Cu) interact with other ingredients or affect formulation stability, specifically with anionic polymers (like carbomers) or surfactants?
3. How can I check the compatibility of ingredients in a formulation?
4. What is the difference between an electrolyte and a metal ion?
5. Does zinc react with fatty acids or should it not be combined with natural oils?
Answer
Here are the answers to your questions regarding Sodium EDTA, mineral ingredients, compatibility, and electrolytes:
- Sodium EDTA and mineral ingredients: Sodium EDTA chelates metal ions, including those from added mineral salts like Zinc and Magnesium. While it will bind these ions, it might still be needed to chelate trace metal contaminants from other sources. Whether it is necessary depends on the formulation goals, the purity of other ingredients, and the desired function of the mineral salts. Chelating the added functional ions might reduce their intended effect, so it's a balance.
- Interaction of mineral salts with other ingredients/stability: Yes, metal ions (Zn, Mg, Cu) can interact with various ingredients and affect formulation stability. They are known to interact strongly with anionic polymers (gelling agents like carbomers) causing thickening or precipitation, and can affect surfactant systems (emulsifiers), potentially leading to instability. Interactions with other ingredients depend on the specific chemicals.
- Checking compatibility: Compatibility information is typically found in technical data sheets (TDS) and safety data sheets (SDS) from ingredient suppliers, scientific literature, formulation guides, and cosmetic chemistry resources. There are general chemical principles, but specific interactions often require testing. The tools available here are not designed to provide general compatibility rules.
- Electrolyte definition: No, electrolyte is not the same as metal ion. An electrolyte is a substance that dissociates into ions (both positive and negative) in solution, making it conductive. Metal ions are a type of positive ion (cation) formed when many electrolytes (like salts) dissolve. They are components of many electrolytes, but the term is broader.
- Zinc reaction with fatty acid/natural oil: Yes, zinc can react with fatty acids to form zinc soaps. This is relevant when formulating zinc compounds with ingredients containing free fatty acids, which can be present in or generated from natural oils. This potential reaction needs to be considered in formulation design and stability testing.