What is Zeta Potential? – 2: Factors Influencing Zeta Potential



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 Factors Influencing Zeta Potential

 

1. pH

In an aqueous solution, the pH of a sample acts as the most significant factor for zeta potential. A zeta potential value without clear solution conditions is practically meaningless.

Consider particles with a negative zeta potential value in a suspension. If more alkali is added to the suspension, the particles will gain stronger negative charges. Adding acid will reach a point of neutrality, and further addition will give positive charges. Therefore, the interaction between zeta potential and pH value is positive at low pH values and low or negative at high pH values.

There are also instances where the value of zeta potential becomes zero, known as the isoelectric point, a critical value for understanding particles.

In general, at the isoelectric point in a colloidal system, minimal stability is maintained. The relationship between typical zeta potential and pH is shown in Fig.8.

 

 

 









Electrophoretic Velocity Measurement

A microelectrophoretic system’s component is a capillary cell with electrodes where a potential difference is present.

As particles move toward the electrode, their speed is measured, representing the particle mobility per unit field strength.

Traditional approaches involve using an ultramicroscope to directly observe individual particles and calculate based on measured distances. Despite being widely used globally, this method has some inconveniences, especially when particles are small or scattering is unstable, requiring substantial effort for measurement.

Malvern’s Zetasizer Nano range of instruments employs laser Doppler electrophoresis with M3-PALS technology.

M3-PALS Technology

The Zetasizer Nano series measures particle electrophoresis using a combination of the patented M3-PALS laser Doppler viscometer and phase analysis light scattering device.

The M3-PALS method can measure samples with very low mobility and calculate their mobility distribution.

PALS is 100 times more efficient than conventional measurement methods.

This technique can accurately measure materials with high electrical conductivity and those with low mobility dispersed in non-electrolytes. It also uses low voltage to avoid drawbacks from Joule heating effects.Additionally, extensive discussions and various papers related to laser Doppler electrophoresis and M3-PALS can be found on the Malvern Instruments website.