This report describes the certification of the equivalent spherical diameters of silica nanoparticles suspended in aqueous solution, Certified Reference Material (CRM) ERM-FD100®. The CRM has been certified by the European Commission, Joint Research Centre, Institute for Reference Materials and Measurements (IRMM), Geel, BE.
The intended use of this ERM-FD100 is to check the performance of instruments and methods that determine the particle diameter of nanoparticles (particle size ranging from approximately 1 nm to approximately 100 nm) suspended in a liquid medium. It is available in 10 mL pre-scored amber glass ampoules containing approximately 9 mL of suspension.
The CRM was prepared from commercially available colloidal silica (Koestrosol 1530, Chemiewerk Bad Koestritz GmbH, DE).
Certification of the CRM included testing of the homogeneity and stability of the ampouled diluted raw material, as well as the characterisation using an intercomparison approach.
The material has been certified for the equivalent diameter of the silica nanoparticles in aqueous suspension using different methods. Certified values are the cumulants dynamic light scattering (DLS) intensity-weighted harmonic mean particle diameter, the line-start centrifugal liquid sedimentation (CLS) intensity-based modal (Stokes) particle diameter, the electron microscopic (transmission electron microscopy (TEM)/ scanning electron microscopy (SEM)) number-based modal particle diameter and the small angle X-ray scattering (SAXS) intensity-weighted average particle diameter.
Indicative values have been established for the volume-weighted mean equivalent spherical diameter via the SAXS method and for the zeta potential via the electrophoretic mobility (ELM) method. Additional informational values are given for the volume-weighted mean diameter via the DLS method, and the pH value of the ERM-FD100 suspension.
Uncertainties are expanded uncertainties estimated in accordance with the Guide to the expression of uncertainty in measurement (GUM) with a coverage factor of k = 2, corresponding to a confidence interval of about 95 %. An exception is the mean equivalent volume-weighted diameter determined by the SAXS method which has a coverage factor of 2.8.JRC.DG.D.2-Reference material
