Interlaboratory comparisons definition

However, does an interlaboratory comparison provide traceability of the results To answer this question, we first look at the definition of traceability and its scientific characteristics. Without a clear, unequivo-... 

There is one thing that we can definitely say is not a source of reference values and that is interlaboratory comparison. Interlaboratory comparison, proficiency testing and the like are very useful tools, depending on the protocols and intended purposes. They can be used to detect and diagnose problems, evaluate competencies and pro-... 

In view of these issues, we have over several years undertaken a substantial research programme to develop definitive methods appropriate for in-house certification of matrix RMs, particularly for analytes at trace levels. These definitive measurement methods, most of which use isotope dilution mass spectrometry (IDMS), been the subject of extensive validation, including CCQM key comparisons and pilot studies involving other national measurement institutes. Hence, we are now able to augment interlaboratory data with data obtained at LGC using these very accurate measurements. We have also... 

This study of methods to determine the moisture content of humic substances has yielded no absolute values for moisture content. The loss on drying shows no end point for water loss and the potential interferences of the Karl Fischer titration prevent definition of absolute values. Certainly, additional research needs to be done in this area. For example, techniques such as NMR and IR might be utilized to define and correlate the moisture status of these substances. In many cases it is sufficient to have a reference point to bring these substances to for comparison purposes. Based on Figure 1, loss on drying at 60°C should be the most consistent reference point, however, the interlaboratory study results showed very poor agreement. Based on this limited study we conclude that the Karl Fischer method gives more consistent results on these samples. 

Boone, J., Hearn, T. and Lewis, S. (1979). Comparison of interlaboratory results for blood lead with results from a definitive method, Clin. Chem. 25, 389. 

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