Reference materials field studies

Frozen reference materials have been produced by NIST (Wise et al. 1993). These materials do not have the disadvantages of the oils or freeze-dried materials, but are more difficult to transport. Obviously they have to be kept deep-frozen during transport, which makes their use rather expensive. Since the early 1990 s a new approach in this field has been introduced. This concerned the use of wet, sterilized fish and shellfish samples. These samples, packed in glass jars or in tins, were firstly used in the QUASIMEME program as reference materials for inter-laboratory studies (de Boer 1997). Later, when it appeared that the stability was maintained for longer periods, tests for organic contaminants based on this principle were also prepared. 

From the available literature it becomes clear that method evaluation studies do not surpass the level of within-laboratory performances. Although several of these (see Table 3.3.1) reveal satisfactory levels of quality and environmentally relevant limits of detection, a genuine quality assurance of these methods is still lacking. There are no reports of interlaboratory studies and certified reference materials for surfactants are not available on the market yet. It can therefore be concluded that there remains much to be done in the field of improving and evaluating quality of analytical measurements of surfactants in biota. 

CIS Chemical Information Systems, Inc., Baltimore, Maryland CESARS Chemical Evaluation Search and Retrieval System 189 chemicals OFFICE OF MATERIALS CONTROL OF THE STATE OF MICHIGAN S DEPARTMENT OF NATURAL RESOURCES Detailed information and evaluations on a group of chemicals of particular importance in the Great Lakes Basin. Each record contains up to 185 data fields with references to the studies used in their documentation... 

The following results summarize the findings of studies carried out by the Forest Pest Management Institute s environmental impact section on a number of chemical insecticides. Significant results from studies conducted by other agencies are referred to in some instances, but no attempt has been made to include exhaustive reviews of all field studies done on each material, as this is well beyond the scope of this paper. 

There are two variables to consider, K and a (the shape factor). If the material being studied and the reference material are molecularly dispersed in a single sample tube (i.e., an internal reference), then there is only one value of k, and both sample and reference molecules experience the same magnetic field. Hence, the effect of magnetic susceptibility can be ignored. 

We acknowledge financial support from the Sixth Framework Programme of the European Union (Contract SSPI-CT-2003-502492 http //www.swift-wfd.com). We also thank Nel Frijns and the RIZA monitoring team in Eijsden (The Netherlands), the local Environmental Agency (in the Aller) for permission to work. Finally, we thank all the partners in the SWIFT-WFD consortium who carried out reference measurements, prepared the reference materials, participated in the proficiency testing and in field studies. 

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