Electrophoretic Light Scattering (ELS) Requirements for Sample Preparation

Electrophoretic Light Scattering (ELS) is an effective technique for measuring the zeta potential of nanoparticles and microparticles. By analyzing the electrophoretic mobility of particles in an electric field, this method provides insights into surface charge characteristics and serves as a valuable tool for evaluating the stability of particle systems. To ensure accurate and reliable measurements, samples must meet specific criteria regarding particle size range, suspension stability, and the absence of sedimentation or flotation. The following sections outline these requirements in detail.

1. First, the particle size should generally be below 120 μm. This limitation arises because ELS measurements depend on the electrophoretic movement of particles, which can be disrupted by gravitational sedimentation if particles are too large. Sedimentation can interfere with electrophoretic signals, compromising the accuracy of zeta potential evaluations. Therefore, maintaining the particle size within an appropriate range is essential for reliable results.
   
   
2. Second, samples must be in a stable suspension. Proper wetting of particles by the dispersant is crucial to forming a stable dispersion, preventing aggregation or floating caused by hydrophobic or oleophobic properties. The dispersant should be selected based on particle characteristics, typically favoring low-viscosity aqueous or organic media. A stable suspension is fundamental for obtaining high-quality measurement data.
   
   
3. Finally, particles must not exhibit significant sedimentation or flotation. Accurate ELS measurements rely on stable electrophoretic motion unaffected by gravitational or buoyant forces. To minimize these effects, the density difference between particles and the dispersing medium should be as small as possible. Additionally, external disturbances, such as flow or vibration, must be avoided to ensure the stability and precision of the measurement signals.
   
   

Conclusion

In summary, ELS measurement requires that particle size remains below 120 μm, samples are in a stable suspension, and particles exhibit no significant sedimentation or flotation. Adhering to these criteria ensures stable electrophoretic motion of particles in an electric field, enabling precise zeta potential measurements.