Chemical water monitoring under the Water Framework Directive with Certified Reference Materials

In the field of environment protection, a series of European Directives with special emphasis on the water bodies has been approved as a cascade after the milestone Water Framework Directive (WFD) of the year 2000.

The most recent piece of legislation, Directive 2009/90/EC, points out the necessity of ensuring the quality of the analytical data and prescribes that the laboratories appointed by the Member States as responsible for the chemical water monitoring shall “demonstrate their competences…by…analysis of available reference materials…”.

Certified Reference Materials (CRMs) are the anchor points for comparability of measurement results, in both space and time, ensuring their traceability to a common reference.

In this article, we present a critical overview of existing matrix CRMs, related to WFD monitoring needs. Our survey concerns available water, biota and sediment matrix CRMs for the 33 Priority Substances (PSs) (and the eight “other certain pollutants”) listed in the WFD, together with a reference to discontinued CRMs. Tables providing a more synoptic view are available on-line as supplementary information.

For the four priority metals (Cd, Pb, Hg and Ni), there are sufficient CRMs for all matrices considered to cover the needs of the monitoring laboratories, but there is a serious lack of matrix CRMs for most of the organic PSs. Also, for the matrix water, there are no materials available for organic pollutants that could be classified as CRMs as commonly understood.

We also briefly discuss pure compounds and solution CRMs for calibration purposes.

In the final section, we show how a CRM could be used in the estimation of measurement uncertainty for checking compliance at the Environmental Quality Standard level, according to the technical specifications given in Directive 2009/90/EC.

Highlights
► Quality and comparability of water chemical monitoring results should be ensured. ► CRMs are necessary for quality assurance and quality control of measurement results. ► Water, biota and sediment matrix CRMs for Cd, Pb, Hg and Ni are generally available. ► There are no water-matrix CRMs for organic priority substances under the WFD. ► Biota and sediment CRMs exist only for some organic priority substances under the WFD.