Matrix Certified Reference Materials for environmental monitoring under the EU Water Framework Directive: An update

Directive 2013/39/EU contains the first revision of the Priority Substances (PSs) list of the Water Framework Directive (WFD). Twelve substances were added, some Environmental Quality Standards (EQSs) in water were revised and biota EQSs for eleven PSs were laid down. The use of Certified Reference Materials (CRMs) can ensure that the water monitoring data be characterised by an equivalent level of scientific quality. In this paper, an updated overview of existing matrix CRMs (water, biota and sediment) for all PSs is presented. Focus is given to the critical discussion of biota CRMs. The range of CRMs for Cd, Pb, Hg and Ni continues to be appropriately large, while the lack of CRMs for the organic substances is confirmed. The CRMs applicability in the light of the WFD monitoring requirements is discussed with regard to matrix match and attributes of the certified value (traceability, uncertainty and closeness to the EQS).