The main distinction of our method for Zeta potential characterization is ability to treat concentrated systems when no dilution applied. We achieve this by using Electroacoustic spectroscopy. International Standard ISO 13099, Parts 1 and 3: 2012 “Colloidal systems – Methods for Zeta potential determination” describes this method.
DTI models for zeta potential
Several models of DTI instruments have this capability but with different options:
- 300 works only for particulates, whereas 310 has titration option included.
- 330 is a universal instrument when both particulates and porous materials can be measured.
- 1202 includes particle size measurement.
All these instruments employ the same Zeta potential probe, which is shown on the Figure below.
Particles content must be above 1 % with particularly no upper limit. There is no restriction on ionic strength.
Ability of Electroacoustic spectroscopy for characterizing concentrated dispersions and emulsions with no dilution and no sample preparation is critical in many cases because dilution affects zeta potential strongly.
There are several DTI Newsletters about zeta potential measurement. Newsletter #2 and Newsletter #5 present general principles and verification tests, whereas Newsletter #7 is about zeta potential titrations of kaolin dispersions, and Newsletter #20 is for cement slurry.
Agreement with electrophoretic method.
Several papers present results of zeta potential measurement when traditional Electrophoretic method and Electroacoustics applied to the same sample. Both methods are in good agreement when dilution follows equilibrium path.
Ishikawa, Y., Aoki, N., and Ohshima, H. “Characterization of latex particles for aqueous polymeric coating by electroacoustic method“, Colloids and Surfaces B, 46, 147-151 (2005)
Hackley, V., Patton, J., Lum, L., Wasche, R.J., Naito, M., Abe, H., Hotta, Y., and Pendse, H. “Analysis of the Isoelectric Point in Moderately Concentrated Alumina Suspensions Using Electroacoustic and Streaming Potential Methods“, J. of Dispersion Science and Technology, 23, 5, 601-617 (2002)
Independence of the zeta potential on the weight fraction of solids.
When comparing our instrument with competing technologies / instruments claiming the same functionality, PLEASE be aware of necessity of having verification tests. Evidently, equilibrium dilution test is the most appropriate for characterizing concentrated systems. The tested instrument should provide the same value of the particle size and zeta potential for various volume fraction of the same concentrated system, when dilution performed with the equilibrium supernate.
Significantly, importance of the equilibrium dilution test has been stressed by the International Standard ISO 13099-1 published in 2012.
We have conducted such tests with variety of dispersions. Results for concentrated TiO2 at 45.9% vl and Silica Ludox TM at 31.2% vl are presented in our book .