ZPi and Zeta Potential

The term “Zeta Potential” applies to the electrical charges existing in liquid emulsions or dispersions of a colloidal nature.

A particle (or dispersed liquid) suspended in a fluid is surrounded by a dense layer of ions having a specific electrical charge. This layer is surrounded by another layer, more diffuse than the first, that has an electrical charge of its own. The bulk of the suspended liquid also has its own electrical charge. The difference in electrical charge between the dense layer of ions surrounding the particle and the bulk of the suspended fluid is the “Zeta Potential”, usually measured in millivolts.
How is Zeta Potential Used?

When ions or polymers are absorbed on a particle in a colloidal system, or by the dispersed liquid in an emulsion, the charge of the layer surrounding the particle is altered. This results in a change in the potential difference between the surrounding layer of ions and the bulk of the suspending fluid. This, by definition, is a change in the zeta potential. The stability of a colloidal system is dependent upon the degree of ion absorption, and, therefore, on the zeta potential. Thus, measurement of zeta potential makes possible the control of processes wherein dispersion or agglomeration is important.

Practically all aqueous colloids are electronegative, with the general range of zeta potential being -14 to -30 millivolts. As the zeta potential is made more negative, the stability of the system is increased. This can be accomplished by the addition of an anionic electrolyte or polyelectrolyte. Zeta potential values more electronegative than -30 mv generally represent sufficient mutual repulsion to result in stability. Stability is assured within a zeta potential range of -45 to -70 millivolts.

When agglomeration is desired, it is necessary to bring the zeta potential closer to zero. This can be achieved by the addition of cationic electrolytes or polyelectrolytes, such as alum or cationic polymers. If the zeta potential is already near zero, agglomeration can be improved further by the addition of long chain polymers capable of producing mechanical bridging between particles.

  • Easy to Use
  • Accurate and Reliable Computer Based Instrument
  • Nanometer Particle Resolution
  • Automatic Sample Handling
  • Interactive Color Monitor Displays
  • Sample Cell Image
  • Zeta Reader Operational Panel with the following digital readouts:
    • Zeta Potential
    • Mobility
    • Specific Conductivity
    • Sample pH
    • Cell Voltage
    • Cell Temperature
  • Optional Image Analysis for particle size distribution
  • Optional Integrated Titration System for easy & controlled chemical additions
  • Optional software for data storage and chart & curve generation with video recording of the cell images

The ZETA-READER has been a respected name in zeta potential measurement since the early seventies. It was designed to be an instrument that would be both simple to use, and give accurate and repeatable results in a wide range of applications. Zeta potential is a measure of the magnitude of the electrostatic or charge repulsion/attraction between particles. Nowadays, even the Common Core curriculum and tests include information about zeta potential.

The new ZETA-READER Mark 21 improves this consistency and dependability by utilizing the latest available technology, while maintaining the original philosophy of flexibility and ease of use.

Our customers played a significant role in our effort to redesign the ZETA-READER, and by integrating their desire for new features and capabilities beyond the original, ZPi has developed a computer based instrument that is completely modular in construction. The ZETA-READER Mark 21 has these following innovative features:

Mark 21 is computer controlled using proven hardware and software that can easily be reconfigured as future advancements are made.

The cell image is scanned by a high resolution color ccd camera and displayed on a high resolution color monitor. ZETA-READER’s original vertical scan lined measuring technique is retained, and with the 25 micron line spacing allows the operator to visually gauge the particle or floc size, while performing tests.

The optical module is designed for the demands of laboratory use, but with the Mark 21’s rugged modular design, it is also easily transported and used in a process environment.

Zeta potential, mobility, specific condutivity, ph, cell voltage, and temperature with full zp compensation are displayed concurrently on the monitor. No switching is required to view the desired parameter.

Light emitting diode (LED) light sources are utilized and offer safe, cool, and extremely long life sample cell illumination in both dark and bright field mode. NO EXPENSIVE AND HAZARDOUS LASER!

The sample cell is designed for quick removal and cleaning or replacement by another cell, with no calibration required, for increased productivity.

Sample flow through the cell is totally automatic. Sample lines are made up of continuous tubes keeping sample volume requirements to a minimum. Extremely small samples may also be injected manually via syringe and automatically purged.

An operation/service manual as well as onboard diagnostics is provided to aid in trouble-shooting or signal tracing.

Optional software is available for data storage and curve generation. Single or multiple curves may be displayed on the monitor with differentiating colored lines, and then stored in the computer file along with the recorded data in the chart form.

Optional Image Analysis for particle size distribution.

Optional Integrated Titration System for easy & controlled chemical additions.