Certification project

The participants The range of participants should, whenever possible, be chosen in such a manner that widely different methods (based on different physical or chemical principles) can be used. The number of participants (recommended 15) should be sufficient to allow meaningful statistical processing of the results. When the laboratories feel the need for a CRM, either because the available calibrants are not comparable and a primary calibrant appears necessary for traceability, or because a reliable certified control material is needed but not available, then it is recommended that these laboratories do not plan a certification project entirely on their own, but that they involve laboratories having a background in traceability. 

Besides the preliminary stability study, regular checks should be carried out over the entire lifetime of the material. In some rare situations over the certification projects conducted under the BCR activities, examples of instability of substances in materials were demonstrated. A typical example was shown by the instability of TBT demonstrated in the CRM 462 (coastal sediment) at +40°C over a short-term period and at +4°C over 24 months which justified the withdrawal of the material from the market and its re-certification (Lamberty et at., 1998). 

Participants were carefully selected among laboratories with a reputation in both the analysis of sediments and active involvement in certification projects undertaken by expert organizations. Representatives of these laboratories were contacted individually to inform them of the planned certification exercise and to encourage their collaboration. In the end, a group sufficiently large was formed that showed much promise for the successful outcome of the project, also because of the wide choice of analytical techniques available. Table 10.1 lists the participating laboratories whose data were accepted along with the techniques used. 

Table 10.1. Laboratories participating in the certification project for trace elements in the CRM MURST-ISS-Al Antarctic Sediment and the instrumental techniques employed...

The overall scheme for conducting the certification project follows the one adopted for the CRM Antarctic Sediment. Therefore, the same general considerations hold and will not be repeated here. Only aspects peculiar to this second instance will be highlighted. 

Twelve vials of the candidate CRM were distributed to each participant in the certification project. All laboratories were free to use the instrumental approach with which they felt more confident and to pretreat the specimens as necessary to adequately present them to the technique of choice. Table 10.4 lists the participants in this project and the techniques used. For the analysis, laboratories were requested to perform complete and independent dissolutions (for techniques requiring the presentation of samples in the liquid form) of the mass contained in five vials (five independent analytical runs, three replicates each). Digestions were to be carried out on different days for each sample. The dissolution of krill was achieved mostly by microwave-assisted acid digestion. 

Figure 10.2. Examples of bar graphs obtained in the certification projects of trace elements in Antarctic krill.

As for Southern Ocean water, steps are being taken to select laboratories with high expertise in the analysis of marine molluscs so as to start with the certification project. 

Guidelines for the production of BCR reference materials, Doc. BCR/48/93 Rart A Recommendations to proposers of BCR certification projects, European Commission DG Xll-C, rue de la Loi 200, 1049 Brussels, Belgium (1994). 

An eel extract and a sewage sludge were prepared and half the extracts cleaned-up by a single laboratory. The second half of the extracts were cleaned-up by each laboratory using the different methods later employed in this certification project in an optimised form. Both sets of samples were analysed for the seven CB congeners to determine the level of variance amongst the clean-up procedures. 

Recently, the synthesis of derivatized standards for ethylation and Grignard derivatization has been carried out at the Free University of Amsterdam " within the framework of an EC-funded certification project (CRM 477) allowing the establishment of optimization and validation studies. The purpose was to prepare highly purified butyltin and phenyltin compounds (in the form of salts) and their ethylated and pentylated derivatives for use as calibration and recovery tests. 

Specific chapters then focus on different projects on speciation analysis. Chapter 4 deals with interlaboratory studies on methylmercury in fish and sediment Chapter 5 describes the collaborative projects to certify organotins in sediment RMs and mussel tissues Chapter 6 gives an overview of the certification project on trimethyllead in simulated rainwater and urban dust Chapter 7 describes the certification project on arsenic species in fish tissues Chapter 8 focuses on the intercomparison and tentative certification of Se(IV) and Se(VI) in simulated freshwater Chapter 9 deals with a feasibility study to stabilize Cr species in solution followed by the certification of Cr(III) and Cr(VI) in lyophilized solutions and welding dust Chapter 10 gives a review of methods used for A1 speciation Chapter 11 develops the overall collaborative project to standardize single and sequential extraction procedures for soil and sediment analysis, followed by interlaboratory studies and certification of soil and sediment reference materials. 

CAST (2001) Rationale for accepting masking MC/DC in certification projects. CAST position paper CAST-6... 

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