Particle size analysis by Laser Diffraction & Dynamic Light scattering
Suspensions or emulsions are made of either solid particles or droplets dispersed in a liquid phase. Particle size will directly impact the overall stability as larger particles will settle faster than smaller ones while smaller particles will have higher tendency to aggregate due Van der Waals attraction forces. Controlling particle size distribution is key in both formulation and QC process to achieve product stability.
AlfatestLab offers particle size analysis from 0,3nm up to 3500 microns for suspensions, emulsions, and powders, as well as method development and method transfer.
Particle charge (Zeta Potential) measurement by Electrophoretic light scattering
The zeta potential of particles is a key indicator of the stability of a colloidal dispersion. Zeta potential depends on both the nature of the particle surface itself and the composition of the aqueous phase. To overcome Van der Waals forces attractive forces between particles high zeta potential value (repulsion forces) is required. Any change in the aqueous phase such as pH, concentration of ions, chemistry, and concentration of surfactant in the formulation will have an influence on the zeta potential therefore on stability.
AlfatestLab can provide Zeta potential measurements of your samples and perform pH and concentration titrations to explore a full range of formulations and assess the best conditions for stability.
Viscosity, visco-elastic and flow properties by rotational rheology measurement
Parameters such as concentration, time, temperature, pressure, agitation, stress, particle size, particle shape, Zeta potential can impact final product flow properties, viscosity and therefore stability. Rheology is an essential technique when testing the long-term stability of dispersions (suspension, emulsion or paste). To avoid e.g. sedimentation, viscosity at low shear rates (simulating samples at rest condition) must be high to slow down the sedimentation process. To avoid phase separation at rest conditions, yield stress is a useful property that can be achieved by adding suitable components in the formulation.
Most liquid dispersions show shear thinning behaviour (viscosity decrease at higher shear rate) often ending to product instability upon specific condition such as shipment. Performing thixotropy test allows to control viscosity profile over time to increase final product stability.
In AlfatestLab our rheology experts are available to set-up dedicated tests to optimise the long-term stability of your products.
Static Multiple Light scattering to offer accelerated aging tests.
SMLS is a consolidated technique for stability analysis allowing to detect and characterize destabilization phenomenon in a concentrated media (sedimentation or creaming layers, aggregates, agglomerates, or coalescence). Being up to 200x faster than conventional shelf life tests SMLS is an ideal tool for screening different formulations and predict which formulation will have longer shelf life hence better stability. The technique provides a unique a stability index that allows to rank samples from the most stable to the least stable based on a single number.
Ask our experts about the technique and how we can provide quick, accurate and objective stability testing.