Quality assurance (QA) for environmental analysis is a growing feature of the nineties as is illustrated by the number of QA guidelines and systems which are being implemented nowadays. There is, however, often a huge gap between the implementation and respect of QA guidelines and the technical approach undertaken to improve and validate new analytical methods. This is particularly true for complex determinations involving multi-step methodologies such as those used in speciation and organic analyses. Quality assurance may also be considered from the technical point of view, which is the focus of this book. The techniques used in different analytical fields (inorganic, speciation and organic analysis) are critically reviewed (i.e. discussion of advantages and limitations) and existing tools for evaluating their performance are described (e.g. interlaboratory studies, use of certified reference materials). Particular reference is made to the activities of the Measurements and Testing Programme (BCR) of the European Commission towards the improvement of quality control of environmental analysis. The book has been written by experienced practitioners. By its nature, it serves as a practical reference for postgraduate students and environmental chemists who need a wide overview of the techniques used in environmental analysis and existing ways of evaluating the performance of relevant analytical methods. The critical discussions of the methods described, as well as the development of quality assurance aspects, makes it unique.