DT-300 passes round robin test for the determination of zeta potential with NIST reference materials
The zeta potential is defined as the electrical potential difference at the shear plan of a moving particle in a liquid medium. Thus, it is a characteristic parameter for the electro-chemical properties of an emulsion droplet or rigid particle in a liquid: it gives some indication on the dispersion stability and the particle mobility in external electric fields. The isoelectric point (IEP), the zero point of the zeta potential is an important value: the particles agglomerate and the dispersion tends to flocculation. The electroacoustic method is using the measured colloidal vibration current (CVI) to calculate the zeta potential of a dispersion (see ISO 13099-3:2014 Colloidal systems – Methods for zeta potential determination).
Within the scope of a round robin test of the „National Institute of Standards and Technology“ (NIST), the reference material NIST SRM 1993 (10 Ma.-% LudoxTM Silica in borate buffer) was measured by a total of 17 laboratories with regard to its zeta potential (download certificate). Among others, a DT-300 was used and two different samples (green and red) were measured 11 times each for verification. All measured values were within the confidence interval of 95 % of the certified value of -56 mV, as the following figure shows:
The DT-300 series instruments are calibrated and qualified with a 10 Ma.-% LudoxTM solution. This is measured with a precision of 3% and even exceeds the requirements of the International Standard „ISO 13099-3:2014 Colloidal systems – Methods for zeta potential determination„.
This successful participation of the DT-300 at the NIST round robin underpins the reliability of the method and the instrument series for the characterization of concentrated dispersions in original concentration. Here you can download the complete report from Dispersion Technology: