The certification of the equivalent spherical diameters of silica nanoparticles in aqueous solution, ERM®- FD101b : certification report

This report describes the production of ERM®-FD101b, silica nanoparticles suspended in an aqueous solution, certified for different equivalent particle diameters. The material was produced following ISO Guide 34:2009. The certified reference material (CRM) was produced by the Directorate F - Health, Consumers and Reference Materials of the European Commission's Joint Research Centre (JRC) in Geel (Belgium). The CRM was produced from a diluted and pH adjusted commercial colloidal silica slurry. Between unit-homogeneity was quantified and stability during dispatch and storage were assessed in accordance with ISO Guide 35:2006. The minimum sample intake for the different methods was determined from the results and information provided by the laboratories that participated in the interlaboratory comparison (ILC) exercises of the characterisation study. The material was characterised for several equivalent particle diameters based on an interlaboratory comparison amongst laboratories of demonstrated competence and adhering to ISO/IEC 17025. Technically invalid results were removed but no outlier was eliminated on statistical grounds only. Uncertainties of the certified values were calculated in accordance with the Guide to the Expression of Uncertainty in Measurement (GUM) and include uncertainty contributions related to possible inhomogeneity and instability and to characterisation. The material is intended for quality control and assessment of method performance. The method-defined certified values are regarded as reliable estimates of the true values and ERM-FD101b can therefore be used for calibration purposes. The CRM is available in 10 mL pre-scored amber glass ampoules each containing about 9 mL of suspension. The CRM was accepted as European Reference Material (ERM®) after peer evaluation by the partners of the European Reference Materials consortium.