Speciation is one of the growing features of analytical chemistry of the 1990s. It is now recognized that the determination of total trace element contents is no longer sufficient - understanding pathways of trace elements depends on specific chemical forms, such as oxidation states, organometallic compounds, etc. However, lack of quality control of speciation often hampers the comparability of data within and between laboratories. Considering the high number of analyses performed by the wide range of EC laboratories, the SM&T programme (formerly BCR) of the European Commission has launched collaborative projects to improve the state-of-the-art of speciation analysis in Europe. This book presents an overview of these recent studies. As well as discussion of the techniques used, their performance as applied to real-case analyses and possible sources of error, the preparation of Certified Reference Materials for the validation of methods used is also described.