Particle Sizing and Zeta Potential
Acoustic and electro-acoustic spectrometer for particle size distribution and zeta potential in concentrated dispersions and emulsions.
When used in conjunction, acoustic and electro-acoustic techniques have significant advantages for characterizing particle size distribution (PSD) and zeta potential (ZP). As such, an optimum ultrasound based technique should combine both acoustic and electro-acoustic spectroscopy together in one instrument. The Acoustic & Electro-acoustic Spectrometer DT-1202 is such an instrument.
The measuring chamber of DT-1202 contains the both acoustic and electro-acoustic sensors. As a result this instrument is capable of measuring an attenuation spectra (see acoustic theory for particle size), as well as Colloid Vibration Current (CVI, see electro- acoustic theory for zeta potential). This instrument can perform acoustic and electro-acoustic measurements separately and independently. At the same time, the interpretation software is quite different for the individual spectrometers, yet provides links between acoustics and electro-acoustics for improved characterization.
For instance, calculation of zeta potential from CVI requires information about particle size distribution, acoustic impedance and sound attenuation. These parameters can be extracted from the acoustic attenuation spectra when acoustic and electro-acoustic spectrometers are combined together. The acoustic spectrometer provides, in this case, the required information about particle size and acoustic properties of the system. This correction is implemented into the DT-1202 software. This software also contains 3 different ways of estimating weight fraction of solids in concentrated sample: 1) from attenuation spectra together with PSD; 2) from attenuation spectra for known a’priori PSD; 3) from the measured sound speed.
The DT-1202 can be supplemented with a set of options which substantially extend this instrument’s capabilities. For instance, it can be supplied with 2 burettes for titration, capable of measuring zeta potential and particle size at different pH, surfactant concentration, and ionic strength. Aqueous and non-aqueous conductivity measurements are also optional. Non-aqueous conductivity is especially important for characterizing zeta potential in non-polar liquids. The Rheological option is suitable for characterizing longitudinal rheological properties, such as compressibility and bulk viscosity. Porous materials Option extends zeta potential capability for these type of samples. This option also includes measurement of porosity with high frequency aqueous conductivity probe.
The DT-1202 has a very flexible sample handling system that we have developed while dealing with complex concentrated systems for over 15 years. This flexibility has been achieved with a set of standard (included) and optional (purchased) Accessories. For instance, in the case of a stable system, sample volume for zeta potential measurements can be as little as 0.1 ml, and for particle size measurement – 10 ml.
There are about 50 papers published by users of the DT-1200, 1201 and 1202 models during last decade. These papers present applications of this instrument for characterizing particle size and zeta potential in a variety of complex systems, and are organized in several groups in the section Applications. Our own studies of particle size distributions and zeta potential with this instrument are given in the section Newsletters.
The DT-1202 Acoustic & Electro-Acoustic Spectrometer provides the capability of both the DT-100 (PSD only) and DT-300 (ZP only) models, packaged together at a more affordable price.
There are 5 US patents that describe several novel and patented aspects of this instrument:
- Dukhin A.S. and Goetz, P.J. “Particle size distribution and zeta potential using acoustic and electroacoustic spectroscopy“, patent USA, 6,109,098 (2000)
- Dukhin A.S. and Goetz, P.J. “Method and device for determining particle size distribution and zeta potential in concentrated dispersions“, patent USA, 6,449,563 (2002)
- Dukhin A.S. and Goetz, P.J. “Method for determining particle size distribution and structural properties of concentrated dispersions“, patent USA, 6,910,367 B1 (2005)
- Dukhin A.S. and Goetz, P.J. “Method for determining particle size distribution and mechanical properties of soft particles in liquids“, patent USA, 6,487,894 B1 (2002)
- Dukhin A.S. and Goetz, P.J. “Method for determining electric properties of particles in liquids by means of combined electroacoustics and complex conductivity measurements“, patent USA, 6,915,214 B2 (2005)