DTI - Model DT-300 - Zeta Potential Probe for Dispersions and Emulsions
DT-300 and DT-310 when titration is included. Zeta Potential Probe at multiple MHz frequencies. Zeta potential probe yields information on following parameters: zeta potential in concentrated dispersions and emulsions (vfr>1%), zeta potential in porous bodies (Model DT-330 and DT-350), electric surface charge density, iso-electric point, optimum dose of surfactant, sedimentation stability of the sample, presence of small amounts of large sedimenting particles.
Advantages over micro-electrophoresis and ELS:
- no dilution, volume fraction up to 50%
- less sensitive to contamination
- higher precision (± 0.1 mV)
- low charges (down to 0.1 mV)
- electro-osmotic flow is not important
- convection is not important
- accurate for non-aqueous dispersions
Models DT-300 and DT-310 have a unique Electroacoustic sensor, which is built as a probe (see on the right) for measuring ζ-potential in concentrates without dilution. The same probe can be used for monitoring sedimentation kinetics.
There is a piezo-crystal inside of the probe that generates sound pulse of certain frequency. These pulses propagate throgh the sample via the gold central electrode. Ultrasound moves particles relative to the liquid, which displaces Double Layers and generates an electric field. This field, in turn, changes the electric potential of the gold electrode. The electric potential of the steel cylinder remains zero because it is outside of the electric field. The Electronics measures AC current flowing between the gold and steel. This Colloid Vibration Current predicted by Debye in 1933 is proportional to electrophoretic mobility, which is in turn proportional to ζ-potential. DTI has verified theory that takes into account both particle-particles hydrodynamic and electrodynamic interactions when calculating ζ-potential from the measured electroacoustic signal.
Equilibrium dilution of rutile dispersion for electroacoustic theory verification in concentrates – ζ potential must be independent of volume fraction if dilution maintains surface-bulk equilibrium.
Example of ζ-potential surfactant titration: three cement samples at 72% wt with incremental additions of three different superplastisizers.
Conductivity aqueous option for measuring electric conductivity of aqueous systems within a range from 10-3 to 10 S/m. This probe functions at MHz range and, consequently, is not affected by electrodes polarization.
Conductivity non-aqueous option for measuring conductivity of various solvents including non-polar liquids within the range from 10-11 up to 10-4 S/m. This option is identical in function to the DT-700 model. This option requires installation of “non-aqueous option”, which is important for protecting instrument sensor from aggressive solvents if they are intended to be used.
External pump for when viscous samples are monitored continuously, which can serve as laboratory prototype for on-line characterization.
Heating control option for temperature titrations.