Electrokinetic analyser for surface potential of planar configurations
The SurPASS electrokinetic analyzer helps scientists in the fields of chemistry and materials science to improve and adjust surface characteristics and to design new specialized material properties e.g. for polymers, textiles, ceramics, glass or surfactants. This instrument enables the investigation of electrokinetic effects at the solid/liquid interface for solids of almost any size and shape. By measuring the streaming potential or streaming current of macroscopic solids, the SurPASS provides the zeta potential as the primary information.
The zeta potential is an interfacial property that is of great importance for understanding the behavior of solid materials in many technical processes. It gives insight into the charge and adsorption characteristics of solid surfaces.
Repeatable – reproducible – reliable
The continuous control of volume flow rate and differential pressure together with a high-precision measurement of streaming potential, streaming current, and cell resistance are crucial for the excellent measuring sensitivity. Integrated routines for plausibility checks increase the reliability of the measuring data.
Fully automated measurement – Titration Unit
With the integrated Titration Unit the zeta potential can be determined fully automatically depending on the pH value or additive concentration in the electrolyte. Two stepper motordriven syringe pumps facilitate high-resolution dispensing of liquids such as acidic or alkaline solutions. The design of the cover for the external electrolyte beaker completes the highprecision titration system.
The SurPASS approach
Zeta potential determination with the SurPASS is based on the measurement of streaming potential and streaming current.
A dilute electrolyte is circulated through the measuring cell containing the solid sample, thus creating a pressure difference. A relative movement of the charges in the electrochemical double layer occurs and gives rise to the streaming potential. This streaming potential – or alternatively the streaming current – is detected by electrodes placed at both sides of the sample. The electrolyte conductivity, temperature and pH value are determined simultaneously.
Electrochemical double layer
The interface between a solid surface and a surrounding liquid shows a charge distribution which is different from the solid and liquid bulk phases. In the model of the electrochemical double layer, this charge distribution is divided into a stationary and a mobile layer. A plane of shear separates these layers from each other. The zeta potential is assigned to the potential decay between the solid surface and the bulk liquid phase at this shear plane. The application of an external force parallel to the solid/liquid interface leads to a relative motion between the stationary and mobile layers and to a charge separation which gives experimental access to the zeta potential.