Available Reference Materials

RMsfor Radioisotopes, Stable Isotopes and Rodiopharmaceuticals 145 Tab. 4.6 Overview of available reference materials for "Am, and °Sr... 

IAEA (1985) [Muramai SU Y, Parr RM] Survey of currently available reference materials for use in connection with the determination of trace elements in biological and environmental materials. Report IAEA/RL/128, International Atomic Energy Agency, Vienna, Austria. 

Those scientists using available reference materials should be encouraged to report such uses explicitly in the scientific literature. A recent article by Jenks and Stoeppler (2001) goes so far as to suggest that scientific publishers should provide explicit recommendations as to how and where in a paper the use of certified reference materials should be described. Proposal and journal article reviewers also need to be encouraged to question the analytical quality control (and ultimate value) of measurements made without the benefit of reference materials. 

There is thus a need for a searchable, ocean science specific, database of currently available reference materials, and one of the recommendations of this report is that such a database be developed and maintained by the ocean science community. 

Analyzing control materials alongside the test samples greatly improves proficiency in mycotoxin analysis. Certified reference materials (CRMs) represent ideal control materials, due to their statement of uncertainty and traceability, and they should be routinely used as much as possible. Unfortunately, as outstanding as the improvements made in the last decade have been, even though the list of CRMs in the area of mycotoxins is rather long, it is still insufficient. A list of the available reference materials in the mycotoxins area is reported in Table 1 the issue has been reviewed by Boenke (27). 

Progress in the fractionation and speciation analysis of elements with the use of extraction is still far from needs and expectations, undoubtedly as a result of the insignificant/insufficient number and small diversity of available reference materials. 

Various sample t es (soil, sediment, biota) from different locations were analysed. In most cases commercially available reference materials were used due to their well-documented sampling conditions and wide variety of sampling sites. Furthermore, bioindicators, especially moss samples were measured. These samples were from higher-contaminated (collected by the Hungarian Nuclear Society in Chernobyl and Pripjaty) and less-contaminated (Hungary and South-France) sites. The sample types, sampling locations and dates are summarized in Table 1. 

Samples must be homogeneous and tested for homogeneity, and should be coded at random, including the two or more blind replicates. A blank or negative control, and, if available, reference materials should be provided. Spiked materials are recommended for recovery study, incurred materials for residues study. 

Many organizations have been involved in developing a traceable accuracy base for analytes of clinical interest (see Chapter 14). A driver for current efforts to develop such a base is the European Directive 98/79/EC on in vitro diagnostic medical devices (www.ce-mark.com/ivd.pdf), which requires that The traceability of values assigned to calibrators and/or control materials must be assured through available reference measurement procedures and/or available reference materials of a higher order. ... 

If in-vitro assays are to be used for total estrogenic load (as effects have been shown to be additive) and as such as a pre-filter for LC-MS analyses, a better traceability in the results is needed. This can be obtained by the use of certified reference materials and participation in inter-laboratory exercises. Unfortunately, there are no commercially available reference materials (which should be natural samples) to date, nor is there any organization of open regular inter-laboratory exercises, which should be given priority in the future. Thus, there are issues which remain to be solved, but initiatives to solve these problems are on the way, so this is hopefully only a question of time. 

The FDA purged the 1984-86 cohort of INDs that did not represent a first commercial filing for the NME. Using available reference materials such as Pharmap-rojects (328) and the Merck Index (267), the FDA verified each IND sponsor was a commercial firm and then checked the Ingredient Dictionary, the Drug Product Reference File microfiche, and its own management information system to confirm that no commercial INDs had been filed for a related compound (salt or ester) prior to the 1984-86 interval. 

In the field of QA/QC the network will check regularly on the availability of methods for high-priority substances and their validation status, and initiate, whenever necessary, the organisation of interlaboratory studies for specific emerging substances. QA/QC information, such as available reference materials, proficiency testing schemes and training programmes for laboratories will be circulated. 

Every analytical laboratory should have its own reference materials for internal quality assurance, and such materials should conform to the same standards of appropriateness, homogeneity and long term stability as are required for certified reference materials (see section "preparation of reference materials). In practice, however, most analytical laboratories do not use their own "in-house" reference materials for internal quality assurance but rather rely on internationally available reference materials. In the opinion of the present author, this is undesirable since much larger amounts are required for internal quality assurance than for externai quality assurance, and thereby the available stocks of expensively prepared certified reference materials will be consumed much too quickly. 

The retention index system has the advantage of being based on readily available reference materials that cover a wide boiling range. In addition, the temperature dependence of retention indexes is relatively small. In 1984 Sadtier Research Laboratories introduced a library of retention indexes measured on four types of fused-silica open tubular columns. The computerized format of the database allows retention index searching and possible identity recall with a desktop computer. Measurement of retention indexes is the basis of the Rohrschneider-McReynolds scheme for classification of stationary phases in GC (see Section 27C-4),... 

Where available, reference materials need to be used for calibration or quality control. The National Institute of Standards and Technology (NIST) and many commercial sources supply such materials. Many high performing technology laboratories are capable of preparing their own reference materials using the same approach used by NIST in certifying their Standard Reference Materials (SRM). The calibration reference materials (RM) should be traceable to national standards, and the traceability must be preserved in the laboratory s documentation system. 

On further improvement, multiple devices are used with a single detector. The signals are then decoded for identifying in the spectral elements. A double beam IR-spectrometer is shown in Fig. 6.30. The incident beam is split into two and one is falling on the sample and another on the reference and compared. Commercially available reference materials are used. 

It is a difflcult task to prepare and maintain reference materials for biomedical samples with trace or ultratrace elements present at their natural level [24]. Most commercially available reference materials for blood, urine, and organs are significantly contaminated with respect to ultratrace elements and are therefore unsuitable for detecting contamination at low levels. Contamination control must therefore be based on replicate analyses of real samples. 

Obviously, the bulk composition of these solid standards should ideally be as similar as possible to that of the samples of interest, because the ablation yield, the transport efficiency of the particles produced, and the generation of the signals in the ICPMS instrument will most probably be influenced by the physicochemical characteristics of the matrix. Unfortunately, perfectly matrix-matched standards are not often available, with the possible exception of the analysis of glass and, particularly, of metals, for which a large number of reference materials are accessible. Some research papers on coins and metallic artifacts have used commercially available reference materials for calibration, generally with satisfactory results [26,39,48,49,63,64,72,73]. 

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