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Model: Wallis

NSX: Cordouan - Pháp

WALLISζTM is an innovative high resolution Zeta potential analyzer purely dedicated to nanoparticle and colloidal charge characterization.

  • Based on a modern version of Laser Doppler Electrophoresis (LDE) technique
  • Ideal tool for studying colloidal suspension’s stability and nanoparticles’ electrophoretic properties

Key benefits

  • No electro-osmosis → Artifact-free measurements
  • Improved LDE technology → Efficient, reliable & simple
  • High-resolution measurement → Accurate & repeatable Zeta potential analysis
  • High durability electrodes → robustness & cost-effectiveness
  • Designed for standard disposable and quartz cuvette → Easy-to-fill, compatible with organic solvents and high-pH suspensions
  • Advanced software functionalities (Time, pH, Temperature kinetic modes, SOPs, reporteditor, etc.)
  • Easy-to-use and intuitive Graphical User Interface (GUI) software

Technologies & innovations

Dip cell : simple, robust, artifact-free

  • Simple and easy sample preparation ; no risk of bubble
  • Robust : high durability vitreous carbon electrodes
  • Artifact-free : optimized dip cell electrodes design → no electro-osmosis bias
  • High resolution measurements : sampling frequency 30 times higher than competitors / significantly improving measurement resolution down to 0,1 mV

Main characteristics

  • Zeta potential measurement range: -200mV to +200 mV
  • High resolution measurement: better than 0.1 mV
  • Dip cell with unique high durability amorphous carbon electrodes
  • ZetaQ proprietary software (lien vers onglet ZetaQ)
  • Compliant with ISO 13099-2 Colloidal system – methods for Zeta potential determination – Part 2

Zeta potential (ζ)

Is a fundamental property of colloidal suspension related to the effective surface electrical charges of particles immersed in a solvent.

ζ measurement is very important because it gives an indication on formulation stability and electrophoretic properties of NPs. Zeta potential is measured by the well-known technique of Laser Doppler Electrophoresis.

Laser Doppler Electrophoresis principle :

An alternative electrical field/voltage is applied between two electrodes immersed deeply in the colloidal suspension; the charged particles are forced into a translation motion (electrophoresis) with a speed (ν) proportional to the applied electrical field. The electrophoretic mobility is defined by the ratio between the particle speed and the applied field amplitude.



Zeta potential range

-500 mV to 500 mV

Mobility range

10-10 to 10-7 m2/V.s

Particle size (For zeta measurement)

1 nm up to 100 µm

Sample concentration

0.0001% to 10% w/% (solvent dependent)

Temperature control range inside the cell

10°C to 70°C +/-0,1°C (depending on cuvette cell material)

Cell options

Cuvette cell with optical quality windows compatible with organic solvents

Sample volume

Typically 750 µL (Hellma cell – 10 mm light path)

Maximum sample conductivity

300 mS/cm

Sample Type

Aqueous & organic solvents – pH: 1-14 (depending on cuvette cell material)

Signal processing

Measurement technology

Laser Doppler Electrophoresis (LDE)

Laser source

Highly reliable 20 mW diode @635 nm coupled to automated optical attenuation system. Other wavelengths available upon request

Measurement angle

Single angle for Zeta potential at 17°

Data processing algorithm

Fast Fourier Transform


Mobility = 10-10 m2/V.s or Zeta = 0,1 mV ( in water)


Avalanche Photodiode – APD


Computer interface

USB 2.0 – Windows XP, Seven


33 cm x 33 cm x 38 cm (HWD)


16 kg


100-115/220-240 VAC, 50/60 Hz, 100 W max

System Compliance

CE certification

ISO 13099-2 : 2012 – Colloidal system – methods for zeta-potential determination – Part 2 : Optical methods