The material selection platform
Cosmetics Ingredients
The material selection platform
Cosmetics Ingredients

Predicting Ingredient Compatibility Using HSP in Cosmetic Formulations

Sander van Loon & Beverley Fricker – Aug 30, 2018

Determination and Application of HSP in Cosmetic Formulations As part of the Fast-Moving Consumer Goods (FMCG) market, the personal care and cosmetics companies strive for innovative concepts and solutions to stand out or stay ahead of a highly competitive industry. Forecasting future trends is clearly a key factor, but as trends are evolving at a very fast pace, adapting market demands into product developments should be as efficient as possible.

Despite the crucial demands of this fast-growing market, trial-and-error methods are still widely used to formulate such products, whereas opting for science-based approaches could offer more controlled product development processes.

In this context, the use of Hansen Solubility Parameters (HSP) is becoming more and more popular, due to their power in predicting and improving compatibility between ingredients in various formulations.

Amongst others, active ingredients are fundamental components of personal care products: even used at very low doses, they are responsible for delivering the claimed benefits. The ever-growing consumer need for highly effective products makes this market one of the most innovation-driven markets, continuously releasing innovative actives. Formulating with such new ingredients can be a challenging task: complete solubility should be achieved to obtain:

 − Stable and homogeneous products
 − Optimize their performance, and
 − Aesthetical aspect (in the case of clear formulations)

While trial-and-error methods are rather time-consuming, applying the HSP approach offers quick and reliable solutions. By determining the HSP’s of the targeted active, optimal oil or solvent blend compositions can be predicted, ensuring its complete solubility, and stability of the formulated product. Besides bringing more efficacy in formulating, HSP gives a further understanding of interactions between ingredients and is just as applicable for solubility as for compatibility.

The predictive power of HSP goes even beyond formulating: HSP’s of the skin have been established, allowing the formulators to target the active delivery onto or through the skin. Let's learn the same in detail:

Smart & Predictive Formulations via Hansen Solubility Parameters

In 1967, Charles Hansen submitted his doctoral thesis “The three-dimensional solubility parameter and solvent diffusion coefficient” which introduces the theory which has since become known as the Hansen Solubility Parameters (HSP). These parameters have removed the trial-and-error process and given practical solutions to countless problems across a wide variety of formulation-based industries (Hansen, 2017).

The term “solubility parameters” is now considered to be quite restrictive, as the use of HSP goes beyond solubility challenges: these parameters can predict the compatibility for various types of chemicals/ingredients, allowing for smart and predictive ingredient matching.

Therefore, HSP should be interpreted as “Hansen Similarity Parameters”, as recognized by Dr. Hansen.

The Hansen Solubility Parameters are made up of δD (Dispersion forces); δP (Polar forces) and δH (Hydrogen bond forces). By plotting these in a 3D space in the HSPiP software, it is easy to visualize and interpret the results. When the HSP have been practically determined, the Compatibility Radius is also provided; all solvents/ingredients within this radius are compatible with the test product. The radius is concentration dependent, the higher the concentration of the product the smaller the radius.

The software HSPiP is now led by Professor Steven Abbott with Dr. Hiroshi Yamamoto. (Abbott, 2017) (Yamamoto, 1999 - Present). VLCI is a certified center for practically determining HSP and has been doing so in close collaboration with Professor Abbott and Dr. Hansen since 2010, for all areas of the formulation world.

To learn more about the fundamentals of HSP, see Professor Steven Abbott’s Article: HSP Science-based Formulation for Cosmetics

Practically Determining Hansen Solubility Parameters

The classic method to practically determine a product’s HSP involves the test material being added to a range of solvents that cover the HSP space. The samples are shaken and left to dissolve. The samples are then visually assessed with a qualitative rank from 1-6, where a 1 means the product is completely dissolved, a 6 means there has been no interaction between the solvent and the product and the other scores indicating various stages of dissolution.

Stages of Dissolution
Stages of Dissolution

This data is then entered into the HSPiP Software, which defines a spheroidal cluster of the solvents that dissolve the test material. This cluster is called the Hansen Solubility Sphere and its central coordinates (δD, δP and δH) define the solubility parameters of the test material. The software also performs an analysis of the “fit” of the data to the parameters it has determined, highlighting the validity of the result, which can indicate if more experimental data is needed.

HSP Sphere
HSP Sphere

This theory can be applied to a wide range of situations, including:

 − Oils
 − Actives
 − Additives
 − Pigments
 − Polymers etc.

In the case of insoluble (crosslinked) polymers or pigments, the scoring is then based on criteria such as swellability or resistance to sedimentation.

VLCI offers the following test methods and HSP workflows for a range of materials and is able to develop bespoke tests for challenging molecules:

Method Suitable for
Dissolution Method Simple solutes, mixtures, additives
Quantitative Swell Test Crosslinked and insoluble polymers
Sedimentation Method Insoluble particles, e.g. pigments
Liquids Method Low molar volume liquids, e.g. solvents

 » Continue reading to explore how to interpret the results out of HSP obtained from various ingredients and thus, learn to implement them in your cosmetic formulation.

1 Comments on "Predicting Ingredient Compatibility Using HSP in Cosmetic Formulations"
Antonieta V Sep 4, 2020
Very interesting!! Thank you for sharing.

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