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Physico-chemical characterization

Predicting ingredient behavior during practical use
Physico-chemical characterization

Physico-chemical tests are used to characterize properties, anticipate behavior in formulation, and measure the performance of Seppic’s ingredients under real usage conditions. Conducted early in the development of a new ingredient, they are essential to optimize the ingredient’s structure or adjust its composition to the functionality and behavior desired by users of end products.

Guarantee the stability of the formulation

From the simple regular monitoring of pH, viscosity, temperature stability, or after centrifugation, to predictive techniques such as zetametry or light backscattering (Turbiscan™), the combination of physico-chemical measurements is used to observe how ingredients affect the stability and robustness of a formulation.

Guarantee the stability of the formulation Example of stability tracking accelerated by light backscattering (Turbiscan™) - it reveals instability phenomena on an emulsion before stabilization

For instance, techniques such as optical or electron microscopy, laser particle size or dynamic light scattering are used to control the role of an emulsifier on the homogeneity and particle size of an emulsion. These techniques help verify the correct distribution of ingredients, such as the right solubilization or dispersion of an active ingredient within the formulation. They can also be used to control the ability of our Montanide™ vaccine adjuvants to stabilize antigenic media over the long term.

Measure performance within the formulation

Physico-chemical tests are often the first step towards measuring an excipient’s performance. Numerous techniques are used, chosen according to the ingredients’s functionality and desired activity.

If the ingredient is a surfactant intended for cleaning, its effectiveness is assessed by measurements of surface tension and wetting properties using a tensiometer or a goniometer. These measures can be supplemented by more specific measures, such as wetting tissue disks if the surfactant is intended for washing laundry in a machine.

If the surfactant is dedicated to the formulation of foam baths, the volume of foam after falling into a test tube is also measured, the objective being to simulate as closely as possible the ingredient’s conditions of use.

The different effects of functional ingredients in cosmetic products can also be measured, such as sun protection factor, water resistance of the protective formulation, coverage or hold of a makeup formula, or even the combability of a hair product.

measuring-combability-hair-product Measuring the combability of a hair product

In the field of excipients for dietary supplements and medications, so-called dissolution tests can be conducted to characterize the properties of excipients dedicated to dry forms for the oral route. These tests aim to measure, for example, the effectiveness of an ingredient in controlling the release of pharmaceutical or nutraceutical active ingredients.

Controlled release of a model active ingredient by Sepismart™ SR Controlled release of a model active ingredient by Sepismart™ SR

Control behavior when using the formulation

A behavior which facilitates the use of the product, such as the easy flow from a bottle, the correct diffusion at the outlet of a spray nozzle, the sampling on the finger in sufficient quantity for a product packaged in a jar, or even proper adhesion of the product to the application area, are all prerequisites for the effectiveness perceived by the user. 

The three techniques of rheology, texturometry and tribology help evaluate how a product behaves in movement, in conditions close to its actual use by the user. They help to control, the behavior of the product. For example, studying the rheological profile of polymers and how they act on the behavior of different galenics (gel, cream-gel, emulsion).

Rheology is the science of the flow and deformation of matter. It is used to study the flow of a product sheared by a rotary movement, in particular the force necessary to trigger the flow, the change in the product’s consistency during movement, and the recovery of the consistency of the product after the shear stop.

Texturometry studies the mechanical properties of a product, its texture, such as firmness/hardness, or adhesion properties when subjected to a translational movement.

Tribology is the science that studies the friction between a product and a surface, as a function of speed, during a rotary movement.

At Seppic, we recently developed an internal method to measure the spreading properties of cosmetic oils in tribology. Using this new method we have identified easily biodegradable alkanes (Emosmart™ V21 and Emogreen™ L15) which compete with the exceptional “glide” of non-volatile silicone oils. This performance was confirmed in sensory tests.