Laboratory reference materials

Progar JJ, May JC, Rains TC, et al. 1996. Preparation of an intra-laboratory reference material-determination of the aluminum content of a pooled 5% albumin (human) solution by ETAAS, MFS and ICP-AES. Biologicals 24 87-93. 

In order to cope with the lack of CRMs for endogenous species, the practice of laboratory internal QC materials is developing. A Laboratory Reference Material (LRM) was prepared from Brazil nuts (Bertholletia excelsa) for QC of the selenomethionine determinations. The concentration of selenomethionine was 79.9 p,g g-1. The homogeneity and stability of this candidate CRM passed the relevant tests recommended by the Measurement and Testing Programme [97],... 

The role and use of reference materials are in principle well known, in particular for Certified Reference Materials (CRMs) used as calibration materials or matrix materials representing - as far as possible - real matrices used for the verification of the measurement process, or (not certified) laboratory reference materials (LRMs also known as quality control (QC) materials) used, for example, in interlaboratory studies or in the maintenance of internal quality control (control charts). Examples of reference materials relevant to WFD monitoring (water, sediment and biota) are described in the literature (Quevauviller, 1994 Quevauviller and Maier, 1999). 

The criteria for the choice of the CRM are not different from the criteria to select the material for the preparation of a laboratory reference material for method development, statistical control charts etc. The difference lies in the availability of adequate CRMs from reliable suppliers and the level of compromise which the analyst must make between an ideal situation and the reality of what is on offer. Massart and co-workers have proposed a principle component analysis to help select the best adapted CRMs available on the market to verify AAS analysis of foodstuffs [10], Their approach took into account the analytes as well as the matrix composition. Besides the fact that they highlighted a lack of sorts of CRM, in particular those having a fatty matrix, they demonstrated that such a statistical approach can help in the most appropriate selection of materials. Boenke also proposed a systematic approach for the choice of materials to be certified for mycotoxins [11] and which could be followed by potential users. The selection of the CRM by the analyst should include a certain number of parameters this can cover the following properties to fulfil the intended purpose level of concentration of the analytes ... 

The needs expressed for CRMs/RMs by the laboratories contacted are very wide and were summarised in the form of a list per analytical sector, as given in Table 5.7. Only clearly identified matrices/chemical parameters are listed. From this table, it can be concluded that the environment and food/agriculture fields generated the largest variety of requests. Other comments were related to the high prices of CRMs and the need for Laboratory Reference Materials fit for purpose to respond to urgent needs (small stock of defined shelf life). More instructions are deemed necessary on how to use the CRMs and better information on suppliers, types of materials etc. is also needed. It seems that many laboratories do not know how to find their way in the broad supply of RMs of very different — and often unknown — quality. 

Beside the needs for RMs and CRMs listed in Table 5.7, many laboratories expressed their wish for more activities in quality assurance/quality control and for teaching on procedures to prepare Laboratory Reference Materials (in-house). They also expressed the need for a larger and better dissemination of information on interlaboratory schemes carried out in Europe (see Table 5.8). In this view, a European directory of existing structures responsible for the organisation of interlaboratory schemes would be most... 

Finally, a series of laboratory reference materials were examined to determine the interlaboratory reproducibility. At each stage, recommendations were made for improvement in the analytical method and are briefly summarised below. 

Reference materials which are prepared for in-house control by the laboratories are often referred to as laboratory reference materials (LRMs) or in-house reference materials (HRMs). 

Analytical quality control measures. RRFs should always be used in conjunction with general analytical QA/QC measures. Precision and other data can be gathered and maintained over time on a consistent, comparable basis. Laboratory reference materials in the form of an extract containing arbitrary levels of all toxins should be used for daily checks on the retention times and responses. Changes in the response ratio analogue/parent may indicate instrument perturbations affecting the RRF. 

NBL - U.S. Department of Energy, New Brunswick Laboratory, Reference Materials Sales, 9800 S. Cass Avenue, Bldg. 350, Argonne, IL 60439, USA... 

MnO, P2O5 were also measured for some samples. The measured X-ray intensities were corrected for matrix effects, absorption, and secondary fluorescence by the Bence-Albee correction program. Results were internally calibrated against international standards, and a laboratory reference material (hornblende) was repeatedly measured to insure consistency between analytical sessions. The results for each point analysis were normalized to total 99.00% (allowing 1 % for water and trace elements) and then the average calculated for each sample (Table 2). 

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