Certified reference materials of soils and sewage sludges for the quality control of trace element environmental monitoring

For the wide variety of soil/sludge matrices encountered in analytical practice, a range of CRMs should be available to verify the analytical quality control of any determination carried out, using samples which should be as similar as possible to real soil and sludge samples so that the method's performance may be tested under real analytical conditions. This paper presents basic requirements for the preparation of soil and sludge CRMs for the quality control of trace element determinations (total and extractable contents, following strict extraction protocols), and gives recent examples of new certifications successfully concluded by the SM&T programme of the European Commission.