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JRC and NIST release two new CRMs for electrophoretic mobility and zeta potential

21 December 2020

The Joint Research Centre (JRC) of the European Commission (EC), in collaboration with the National Institute of Standards and Technology (NIST), produced its first Certified Reference Materials (CRM) for electrophoretic mobility and zeta potential measurements by electrophoretic light scattering (ELS). The two CRMs may contribute to the REACH classification of nanoforms, as zeta potential is an essential physicochemical parameter for the characterisation of nanoforms.

Zeta potential is regarded as the most important characteristic to predict the stability of a dispersion of particles, i.e. whether particles stay dispersed or whether they aggregate and/or agglomerate. This makes the zeta potential a crucial parameter to assess the suitability of a nanomaterial for a specific purpose. Zeta potential is calculated from the electrophoretic mobility of a material. Currently, two methods are mainly used, namely electrophoretic light scattering (ELS) and acoustophoretics. Despite the widespread use of these methods, no reference materials allowing traceable calibration of acoustophoretic instruments are currently available and there is also a lack of negatively charged particle reference materials (only the positively charged particle NIST SRM 1980 is available) to assess the measurement accuracy of electrophoretic light scattering instruments.

Two colloidal silica based certified reference materials (CRMs) for electrophoretic mobility/zeta potential measurements were developed for both ELS and acoustophoretics (electroacoustic instruments). This work was a joint effort between JRC and NIST that was initiated through the ISO Technical Committee for Particle Characterisation (ISO/TC24/SC4) at the request of industry. The CRMs are jointly released by both institutions. The first CRM (ERM-FD305/SRM 1992), developed for electrophoretic light scattering methods, was produced at a suitable particle concentration for optical-based instruments and for use as a quality control material. The same colloidal material at a higher concentration (ERM-FD306/SRM 1993) was produced for electroacoustic methods to be used as a calibration standard to convert the measured signal to zeta potential.

The CRMs were processed and certified in accordance to with ISO 17034:2016 and ISO Guide 35:2017. Details about material sampling, processing, characterization and are described in the certification reports, available together with the certificate in the dedicated product pages for ERM-FD305 and ERM-FD306.
See also the announcement by NIST here.

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