Nov 21 2009
A new application note, freely available on the Malvern Instruments’ website, describes how the new ZEN1010 high concentration zeta potential cell for the company’s market-leading Zetasizer Nano particle characterization system, overcomes a major hurdle in measuring the zeta potential of high concentration samples. Taking the notoriously difficult to measure titanium dioxide as an example, the authors describe experimental work that demonstrates accurate and reliable zeta potential measurement of concentrated, turbid suspensions.
This ability to measure the zeta potential of more concentrated samples than has previously been possible is thanks to the reduced optical path length of the new ZEN1010 cell, and has applications for a very wide range of materials. The application note can be downloaded at www.malvern.com/titaniumdioxide
Because of its high refractive index, titanium dioxide is widely used as a pigment in products such as paints, coatings, paper, food and cosmetics. To perform optimally, the titanium dioxide particles must be properly dispersed and maintained in suspension, and a key parameter used to study dispersion behaviour is zeta potential. This parameter is measured using the technique of laser Doppler electrophoresis, which normally requires samples to be optically clear. The new ZEN1010 cell, however, features an optical path of reduced length, which compensates for the issues of reduced light scattering detection experienced with standard cells when measuring high-concentration samples.
Although it is used in the same way as a standard cell on the Zetasizer Nano, the ZEN1010 allows robust zeta potential measurements in highly concentrated samples. By requiring less sample dilution, it more closely preserves the pH and chemical structure of the sample, for more directly relevant zeta potential measurements. This is especially important for many colloidal materials, where measuring the sample in its native state avoids the need for the often complicated centrifugation and dilution procedures needed to maintain sample integrity.