CERTIFICATION REPORT The certification of the mass fractions of C, H, N and O in the certified reference materials ERM-EB090a and ERM-EB090b

This report describes the certification of the C, N, H and O mass fraction in the CRMs ERM-EB090a and ERM-EB090b, which are titanium materials that were certified for their trace element mass fractions in 2018. Also the new values for C, H, N and O were certified in accordance with ISO 17034 and ISO Guide 35:2017. Between unit-homogeneity was quantified in accordance with ISO Guide 35:2017. The minimum sample intake was derived from the sample intakes of laboratories participating in the characterisation study. Based on the nature of the material, potential uncertainty for degradation during transport and storage is negligible. The material was characterised by an interlaboratory comparison of laboratories of demonstrated competence and adhering to ISO/IEC 17025. Technically invalid results were removed but no statistical outlier was eliminated unless a technical reason for the deviation was found. Uncertainties of the certified values were calculated in accordance with the Guide to the Expression of Uncertainty in Measurement (GUM) and include uncertainties related to possible inhomogeneity, instability and characterisation. The materials are primarily intended for the quality control and assessment of method performance. As with any reference material, they can be used for establishing control charts or validation studies. The CRMs are available in discs (ERM-EB090a: diameter 40 mm; height 20 mm; approximately 115 g) and 7 g of metal chips contained in glass vials (ERM-EB090b). The minimum sample intake representative for C is 150 mg and for H, N and O 50 mg.JRC.F.6-Reference Material