5. Conclusions

Over the last few decades, analysts have first been led to set up laboratory quality assurance systems in specific forms, such as the accreditation standard ISO IEC 17025 or good laboratory practice (European directive). In this way, method validation has become a central and essential element in demonstrating a laboratory's competence and its ability to provide its customers with "quality" results. Metrology has also undergone a major change in the way results are expressed: they are no longer considered as a single true value, but as a set of true values for the measurand. This set can be expressed using what is known as an extended interval. To obtain this type of interval, it is essential to have an estimate of the uncertainty of measurement, whatever the value of the object being measured. In analytical chemistry,...