How We Measure Colloids

At Colloidal Dynamics we measure the size and zeta potential of the particles in a colloid - dynamically.

We use two techniques to do this.

With our patented Electroacoustic Method we apply an alternating electric field to force the particles in the colloid to move back and forth in a high-frequency oscillation. This particle movement results in sound waves, which we analyze to determine particle size and zeta potential. Measurements are made over a range of frequencies from 1 to 20MHz in the AcoustoSizer and 300 kHz to 3 MHz in the ZetaProbe

In the AcoustoSizer we complement the electroacoustic technique by making Ultrasonic Attenuation measurements. In this technique we determine the amount by which a sound wave is attenuated as it crosses the colloid. From the measurement of this quantity as a function of frequency we get the particle size distribution.

A key benefit of these techniques is that we can measure when the colloid is undiluted, in its dynamic industrial environment.

Our approach is acoustic rather then optical. Because most colloids in industry are concentrated and opaque, optical methods for measuring size and zeta require sampling and dilution procedures separate from the industrial process. Dilution can completely alter both the size and zeta potential of a colloid.

We analyze colloids in situ, without interrupting the underlying industrial processes. Measurements can be made on flowing colloids.

Both particle size and zeta potential are important characteristics of a colloid:

  • The size and zeta potential of the particles in a colloid determine many of the characteristics of the colloid.
  • The optical qualities of pigments are affected by the particle size of the pigment.
  • The rheology (flow) of a colloid depends on zeta.
  • The shelf life and settling volume of a colloid is affected by the zeta.
  • Both size and zeta alter the effectiveness of de-watering and filtering processes.
  • Particle size is a factor in the efficacy of colloid-based pharmaceuticals.
Read this article on our measurement techniques (PDF 458Kb)