Particle Size,

Shape and Charge

Repulsion Analysis

Micromeritics Analytical Services (MAS) has the most extensive portfolio of particle sizing capabilities in the industry

Our contract services include more than 6 different sizing techniques to address any particle sizing challenge or application specific need you may encounter. Our staff has the experience and scientific knowledge to assist you in interpreting the results so you have rich data to make appropriate decisions.

Particle Sizing via Dynamic Light Scattering (DLS)

Used for nano-particle characterization, Dynamic light scattering determines particle size by measuring the changes in intensity of light that is scattered from the Brownain motion of diffusing particles in a liquid suspension or solution. The larger the particle the slower the Brownian motion. Preferred method for more highly particle concentrated solutions than static light scattering measurements.

Available instruments:

  • Particulate Systems NanoPlus HD

Particle Sizing via Static Light Scattering

The Laser Light Scattering Technique utilizes Mie and Fraunhofer Theories to determine particle size distribution from a light scattering pattern. The smaller the particles the higher the contribution of refraction and absorption to the static light scattering pattern Typical range of measurement is 0.02 um to 2000 um.

Available instruments:

The X-Ray Sedimentation Technique

The X-Ray Sedimentation Technique takes advantage of the natural tendency of particles to separate by size as they settle through a liquid medium. The mass fraction in each size class is determined by the adsorption of soft X-rays. This method produces excellent resolution where the particle size distribution is narrow. Measure range is 0.1 um to 300um.

Available instruments:

Electrical Sensing Zone

The Electrical Sensing Zone Method commonly known as the Coulter principle, employs an electrical circuit created between two electrodes immersed in an electrolyte on opposite sides of a small orifice. An electrical signal proportional to the volume of the particle is produced as particles are swept through the orifice by a flow of the electrolyte. The technique is used both to measure particle size and to determine particle concentration by counting particles in a solution.

Particle size range is 0.5um to 300um

This is an excellent approach as an orthogonal method to more established light scattering techniques and is not subject to the shape and optical properties of particles as with light obscuration techniques.

Available instruments:

Air Permeablity Particle Sizing

This technique uses the principle of pressure drop across a packed bed of powder. By varying the sample height, and hence the “porosity” of the bed, average surface area and particle size can be determined as a function of pressure drop and flow rate in accordance with the Carmen equation. The SAS measures particle size in the range of 0.2 µm to 75 µm and has a compression accuracy of less than 0.05 mm. This method produces results that correlates identically to the established Fisher numbers.

Available instruments:

  • Micromeritics SAS Subsieve AutoSizer

Sieves Analysis

Particles are subjected to horizontal or vertical agitation. This movement causes particles to either be retained on the mesh opening of the sieve or passed through. Passage of the particle is dependent on the size of the sieve opening, the orientation of the particle and the number of encounters of that particle with the sieve surface. The particle diameter measurement range is 45 um to 10 mm.

Available instruments:

  • Tyler Ro-Tap RX-29

SEM-Scanning Electron Microscopy

The SEM is an analytical tool that uses a focused beam of electrons to form magnified images. Both topographical and compositional information can be obtained with high spatial resolution in a real-time analysis. Image analysis by SEM can resolve individual primary particles from agglomerates and provides a direct measurement of the particle itself as well a particle distribution when processed through available SEM software.

Available instruments:

Particle Shape Measurement

Particle Shape effects often have a significant influence on final product performance parameters such as flowability and spray patterns for inks and toners, abrasive efficiency, and bio-availability.

Shape is particularly important as a qualifying parameter for confirmation of particle sizing analysis based on light scattering and obscuration methods as these techniques use the basis that all particles are spherically shaped, which is not the case.

Micromeritics Analytical Services uses optical microscopy, scanning electron microscopy, and dynamic image analysis to report particle shape parameters.

Dynamic Image Analysis is an automated technique which uses a high-resolution CCD camera to capture images of particles as they pass through a detection zone. Once this image has been captured we can apply different shape parameters to calculate a particle size distribution.

Available Instruments: 

Light Obscuration

This technology works with dilute concentration of particles in a liquid suspension. The suspension is passed between a laser light source and a detector. The laser illuminates the individual particles in the stream and results in a shadow or blockage of light on the detector. This light blockage is termed obscuration. The detector measures this reduction in light intensity and using a calibration curve, processes the signal to determine the size of the particle and the concentration of the sample. The particle size range is 0.5 to 400 micrometers.

This technique is specifically useful in USP methods <788> and <789> for detecting particulates in injectable solutions.

Available Instruments: 

  • Particle Sizing Systems Accusizer Model 770

Zeta Potential-Charge Repulsion Measurement

Zeta potential is a measure of the magnitude of the electrostatic or charge repulsion/attraction between particles. Zeta potential depends on the properties of the liquid as well as on properties of the particles. It plays an important role in determining the aggregative stability of the solution or emulsion. The greater the zeta potential, the more robust the repulsion, the more stable the system becomes.

Available instruments:

  • Particulate Systems NanoPlus HD-3