The participation in interlaboratory studies and the use of Certified Reference Materials (CRMs) are widely recognised tools for the verification of the accuracy of analytical measurements and they form an integral part of quality control systems used by many laboratories, e.g. in accreditation schemes. As a response to the need to improve the quality of environmental analysis, the European Commission has been active in the past fifteen years, through BCR activity (now renamed Standards, Measurements and Testing Programme) in the organisation of series of interlaboratory studies involving...