M3 technique for zeta potential measurement

Citation

(2001), "M3 technique for zeta potential measurement", Pigment & Resin Technology, Vol. 30 No. 2. https://doi.org/10.1108/prt.2001.12930bad.008

M3 technique for zeta potential measurement

M3 technique for zeta potential measurement

Keywords: Malvern Instruments, Analysis, Sizing, Particles

M3 (Mixed Mode Measurement) is a new, patented technique for measuring zeta potential using electrophoresis, which Malvern Instruments is introducing in the latest Version 1.51 software for the Zetasizer system. It uses a combination of the best features of measurement at the stationary layer and the recently described Fast Field Reversal (FFR) technique, to provide what is claimed as unprecedented accuracy and resolution.

Using M3, the entire zeta potential measurement procedure is said to be simplified. The number of measurement variables is reported to be significantly reduced, resulting in improved day-to-day repeatability and greater measurement accuracy. The nature of the measurement technique also means that cell positioning is no longer a concern.

The robustness of the technique is believed to make it ideal for comparative studies over prolonged periods. Improved resolution reportedly allows mixtures of partially coated and fully coated materials to be resolved, including coated latices for diagnostic kits. In addition a high-resolution mode can be used to follow the interaction between materials with different zeta potentials.

Malvern also informs us that it has introduced its Sysmex FPIA-2100, a fully automated particle size and shape analyzer that Malvern believes is set to change the way particles are analyzed. The company considers that, until now, the absence of a universal shape analysis technique has created difficulties in associating the function of particles with their shape characteristics, a problem that the new system is designed to solve.

Particle geometry, as well as size distribution, affects the characteristics and behaviour of particulate materials (in toner and powdercoatings manufacture for instance).

The FPIA-2100 uses patented technology which, as the result of experience in Japan, is already being written into a number of toner manufacturers' patents. The new system reportedly delivers particle size and shape distribution and, using a CCD camera, produces images of each particle as well as a scattergram of shape index versus particle size – in just five minutes.

Samples pass through a sheath flow cell that transforms the particle suspension into a harrow or flat flow, ensuring the largest area is oriented towards the camera and that all particles are in focus. A CCD microscope illuminated by strobe captures particle images (every 1/30 second) which are analyzed in real time. The system claims to measure the size of particles from 0.7µm to 160µm.

Numerical evaluation of particle shape is derived from measurement of the area of the particle. From this can be determined its perimeter, circularity (shape index) and circle equivalent diameter.

Plate 3 Sysmex FPIA-2100 particle size and shape analyser

The FPIA is thought to be simple to use, with automatic cleaning, checking and running of blank sheath reagent on power up. Using Windows 95, the FPIA-2100's software is powerful and straightforward. It stores up to 600 measurements, including particle images, and offers comprehensive analysis and display parameters together with options for data output (Plate 3).

Details available from: Malvern Instruments Ltd. Tel: +44 (0) 1684 892456; Fax: +44 (0) 1684 892789; e-mail: diptil@malvern.co.uk