Certification of the mass concentrations of calcium, chloride, magnesium, ortho-phosphate, potassium, sodium and of pH and conductivity in groundwater : Certified reference material ERM-CA616

This report presents the preparation and certification of the groundwater certified reference material ERM-CA616. All the steps required for the production of this water-matrix certified reference material are described in detail, from the sampling of natural groundwater until the characterisation exercise that lead to the final assignment of the certified values, following ISO Guide 34:2009 1 and ISO Guide 35:2006 2. Homogeneity and stability of the water material were investigated with dedicated studies and the certification campaign for the material characterisation was based on an inter-comparison among several experienced laboratories. IRMM organised and coordinated all the phases of this project and carried out the evaluation of data. The certified values were calculated as the unweighted mean of the laboratory means of the accepted sets of results for each parameter. Uncertainties were calculated in compliance with the Guide to the Expression of Uncertainty in Measurement (GUM, ISO/IEC Guide 98-3:2008) 3. The stated expanded uncertainties include contributions from characterisation, homogeneity and stability