This report describes the production of ERM-BD512, which is a matrix material certified for the mass fraction of cadmium, copper, manganese and nickel. This material was produced following ISO Guide 34:2009 and is certified in accordance with ISO Guide 35:2006.
The CRM was produced from commercially available dark chocolate produced in Peru. About 15 kg of chocolate bars were melted, the melt was homogenised and cast into moulds to produce pellets of about 0.5 g.
Between unit-homogeneity was quantified and stability during dispatch and storage were assessed in accordance with ISO Guide 35:2006 [ ]. Within-unit homogeneity was quantified to determine the minimum sample intake.
The certified mass fraction of Cd was obtained by measurement, using the technique of isotope dilution ICP MS. The mass fractions of Cu, Mn and Ni were obtained by an interlaboratory comparison of laboratories of demonstrated competence and adhering to ISO/IEC 17025:2005. Technically invalid results were removed but no outliers were 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 uncertainties related to possible inhomogeneity, instability and characterisation.
The material is intended for quality control and assessment of method performance. As with any reference material, it can be used for establishing control charts or validation studies. The CRM is available in packages of 6 glass vials, each containing a single pellet of about 0.5 g, which were sealed under an atmosphere of argon. The minimum amount of sample to be used is 250 mg.
The CRM was accepted as European Reference Material (ERM®) after peer evaluation by the partners of the European Reference Materials consortium.