The starting material was 1500 L of seawater collected at Southern Bight just inside of Belgian territorial waters. The sample was filtered, acidified and spiked before filling into 500 mL high density polyethylene (HDPE) bottles which were placed into an aluminised PET/M (metallized polyethylene terephthalate) sachets. The material was sterilised by gamma irradiation.
Between unit-homogeneity was quantified and stability during dispatch and storage were assessed in accordance with ISO Guide 35:2006. Due to the inherent homogeneity of filtered water samples, determination of minimum sample intake (within-unit heterogeneity) was not required. The material was characterised by an inter-comparison among laboratories of demonstrated competence and adhering to ISO/IEC 17025:2005. 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, and instability and to 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. The certified reference material (CRM) is available in bottles containing 500 mL of seawater. The CRM was accepted as European Reference Material (ERM®) after peer evaluation by the partners of the European Reference Materials consortium.
keywords: environmental materials , natural water , seawater , trace elements , heavy metals