A buffer system normally consists of a weak acid and its conjugate base, or a weak base and its conjugate acid. Its purpose is to maintain the formulation within a relatively stable pH range.

pH is important in cosmetics because it can affect skin compatibility, preservative efficacy, polymer viscosity, emulsion stability and the chemical stability of active ingredients.

Common buffer systems used in cosmetic formulations include citrate, phosphate, lactate and other organic acid-based systems.

Buffer Capacity

Buffer capacity refers to the ability of the system to resist pH change. A buffer with insufficient capacity may not adequately control pH drift, while excessive buffering can make formulation adjustment unnecessarily difficult.

The appropriate buffer system depends on the desired pH range and the formulation composition.

Formulation Considerations

Buffer components can interact with other ingredients. Electrolytes may affect polymers, emulsifiers and preservation systems, while pH changes may alter the ionization and solubility of active ingredients.

For this reason, the buffer should be evaluated in the complete formulation rather than only in a water solution.

References

Barel, A. O., Paye, M. and Maibach, H. I. Handbook of Cosmetic Science and Technology. CRC Press.

European Commission. CosIng – Cosmetic Ingredients Database.

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