Metrology in Chemistry

The adoption of ISO/IEC 17025 brings with it a number of new challenges in terms of technical issues in laboratories, notably those relating to traceability and measurement uncertainty. Many laboratories would have wondered whether it is all worth the angst and what real improvements can be realised through addressing these issues in the standard.

Some basic definitions in metrology

Metrology is defined as the science or study of measurement. Most laboratories are involved in making measurements, so it is a term applicable to almost all scientists.

The definition for traceability is currently undergoing revision. At present it is defined as “the property of the result of a measurement or the value of a standard whereby it can be related to stated references, usually national or international standards, through an unbroken chain of comparisons all having stated uncertainties” (VIM, 1993).

Measurement uncertainty is defined as a “parameter associated with the result of a measurement that characterises the dispersion of the values that could reasonably be attributed to the measurand” (VIM, 1993). Simply expressed, it is the range in which the true result lies.

Together, the attributes of traceability and measurement uncertainty help to define the quality of a measurement result for users of this data.

Why bother with Metrology in Chemistry?

For many decades, scientists making physical measurements, such as dimensional determinations, have taken care to establish the metrological characteristics of the measurement system. Over the past decade or more, chemists have come to the realisation that the concerns of the physical measurement scientists in terms of the determination of traceability of measurements and the associated estimation of measurement uncertainty are relevant and it is entirely feasible to determine these attributes of chemical measurement systems. The benefits of explicit understanding of a measurement system are many and include improvements to the measurement process and greater understanding by the users of the quality of the results produced by laboratories.

However, chemical measurements are certainly often more complex than physical measurements, with due consideration needed in regard to both the identity of the analyte of interest in the sample and how much of the analyte exists in that sample. It is therefore important that those engaged in metrology in chemistry have a sound understanding of chemistry and the concepts of traceability and measurement uncertainty, as well as the approaches available for the estimation of measurement uncertainty. At MAS Management Consultancy Services, our staff have skills in Chemistry and a practical understanding of the concepts of metrology and how these are used in a chemistry environment. We can provide training to your staff in this area and assist you to implement the requirements of ISO/IEC 17025 with respect to metrology.

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