The material was produced following ISO Guide 34:2009.
Approximately 500 litres of surface seawater were collected from The Netherlands and transferred into a pre-cleaned polyester tank. Upon arrival at the JRC Geel, the water was acidified and passed first through a 0.8 ìm, then through a 0.45 ìm filter into another pre-cleaned tank. After filtration, the water was spiked with Hg2+ to achieve a final concentration of total Hg of approximately 20 ng/L. Aliquots of 100 mL were dispensed into borosilicate glass ampoules which were flame sealed and sterilised by gamma ray irradiation.
Between ampoule-homogeneity was quantified and stability during dispatch and storage were assessed following ISO Guide 35:2006. The material was characterised by means of an inter-comparison among laboratories of demonstrated competence and adhering to ISO/IEC 17025 for Hg and by a primary method of measurement, confirmed by independent results for density. Technically invalid results were removed, but no outlier was eliminated on statistical grounds only.
Uncertainties of the certified values were calculated in compliance 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 the quality control and assessment of method performance. As any reference material, it can also be used for control
charts or validation studies.
keywords: environmental materials , natural water , seawater , trace elements , heavy metals