Particle analysis of oil-in-water emulsions

Oil-in-water emulsions are widely used, from pharmaceuticals to beverages, paints to speciality chemicals and more. An emulsion is basically a simple system of two immiscible liquids forming droplets. One of the most important properties to control is stability, which can be affected by external factors such as storage, time, temperature, osmolarity, pH, surfactants and shear stress. Weak stability can especially alter droplet size (e.g. by fusion) which can have important consequences for the taste of a soft drink or the effectiveness and safety of a pharmaceutical product.

About Classizer™ ONE

Particle analysis is crucial in the formulation and quality control of oil-in-water emulsions. It enables the investigation of particle growth and stability. Classizer™ ONE provides valuable assistance in the characterisation of oil emulsions. The SPES data provides both physical and statistical information, such as particle size distribution (PSD), oversize, effective refractive index and an estimate of emulsion behaviour and stability. This information is essential for improving the knowledge and quality of oil in water formulations.

Benefits of Classizer™ ONE in the formulation and quality control of oil-in-water emulsions:

Characterises particle size, charge, stability and concentration of emulsions.

Measures particle size and concentration in heterogeneous liquids.

Estimates scale thickness and charge capacity.

Reduces formulation time and costs required to bring new products to market.

Optimises effectiveness and improves stability of formulations.

Figure right

EOS CLOUDS of a silicone oil-in-water emulsion. EOS software automatically estimates an RI of 1.40 in line with the expected value.

Figure left

EOS CLOUDS of a mineral oil-in-water emulsion. EOS software automatically estimates an RI of 1.47 in line with the expected value.

Example: Mixture of two emulsified oils

A more complex situation is the presence of multiple oils of different refractive index in the same liquid. An example is a mixture of two emulsified oils.

Figure right: EOS CLOUDS from a mixture of two oil emulsions with different refractive indices (1.40 and 1.47). Two separate data ‘clouds’ are observed, indicating two separate oil emulsions populations in the water.

Example: Emulsion of a mixture of oils

Another complex case is when several oils are present in suspension in a single drop. This involves an emulsion of oil mixtures with different concentrations. If the oils are mixed before emulsification, both oils are present in the droplets suspended in the liquid. The significant optical parameter, namely the refractive index (RI), of the emulsion is the weighted average of the RIs of the two oils.

Figure left: EOS CLOUDS of a mixture of two oils with different refractive indices (1.40 and 1.47) emulsified in water. A single data cloud is observed. The software calculates an effective mean RI of 1.44.

Figure right

Measured refractive index of the emulsions based on the percentage of starting oils of the mixture (with RIs of 1.40 and 1.47, respectively).

The different positions in the EOS CLOUDS for the blends give an estimate of the initial concentrations of the oils.

More information on particle analysis of oil-in-water emulsions?

Contact Inventech for more information

Particle analysis of oil-in-water emulsions l Inventech

CLASSIZER™ ONE is an ideal tool for characterising oil-in-water emulsions.