The main distinction of our method for Zeta potential characterization is ability to treat concentrated systems as is, with no dilution. We achieve this by using Electroacoustic spectroscopy , which is described in the International Standards ISO 13099, Parts 1 and 3: 2012Colloidal systems – Methods for Zeta potential determination :http://www.iso.org/iso/catalogue_detail.htm?csnumber=52807
There are several models having this capability: DT-300 (zeta only), DT-310 (titration included), DT-330 (universal probe for particulates and porous materials) DT 1202 (with size).
Particles content must be above 1 % with practically 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 dedicated to the zeta potential measurement. Newsletter # 2. and Newsletter #5. present general principles and verification tests. Newsletter #7. is about zeta potential titrations of kaolin dispersions. Newsletter #20, is for cement slurry.
Agreement with electrophoretic method.
There are several papers presenting results of zeta potential measurement using traditional electrophoretic method and Electroacoustics. Good agreement can be achieved between this methods if dilution of the sample required for electrophoresis is conducted with equilibrium supernate.
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)
Tassel van J., Randall, C.A. “Surface chemistry and surface charge formation for an alumina powder in ethanol with addition of HCl and KOH”, JCIS, 241, 302-316 (2001)
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. 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, IF dilution performed with the equilibrium supernate. Failure to provide such tests from the highest to the lowest limit of the claimed concentration range, means that such instrument is not validated.
Importance of the equilibrium dilution test has been stressed by 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.