Uncertainty Principle in Conformity Assessment of Chemical Composition of a Substance or Material

Ilya Kuselman, Consultant, Modiin, Israel (ilya.kuselman@gmail.com)

Conformity assessment of chemical composition consists in comparison of measured values of contents or concentrations of components of a substance or material with their specification limits described in a standard or another regulatory document. The specification limits are set based on an experience, i.e., also on measured values - experimental data accumulated in the corresponding scientific study, during manufacturing and use of the substance or material.

Similar to the Heisenberg’s principle in quantum physics (we cannot know with perfect accuracy both the position and speed of a particle, such as a photon or electron), it is impossible to know also both the measured value and the specification limit with perfect accuracy. Moreover, comparison of a measured value with the specification limit taken as the true value, is still influenced by the measurement uncertainty associated with the measured value.

When a multicomponent substance or material is under conformity assessment, the decision on conformity or nonconformity may be influenced also by correlations between the contents or concentrations as measurands and their mass balance constraint. Measured values in such a case are interdependent as well, even if there is no a metrological reason for that.

Thus, the uncertainty principle in conformity assessment of chemical composition is that a decision on conformity or nonconformity cannot not be certain, and risks/probabilities of false decisions are never equal to zero. 

A background for understanding the risk evaluation techniques, developed in framework of the IUPAC projects, will be explained in the lecture.

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Short Biography of Presenting Author

Ilya Kuselman, https://orcid.org/0000-0002-5813-9051, has received his PhD in inorganic chemistry from Kalinin State University, and DSc in analytical chemistry – from R&D Institute for Rare Metal Industry, Moscow, Russia. Since 1971 to 1990 Ilya has been a researcher and then Head of Metrology in Chemistry Division of All-Union R&D Institute of Non-ferrous Secondary Metals, Donetsk, Ukraine, former USSR. Since 1991 to 2014 he was a co-worker and further Director of the National Physical Laboratory of Israel. Now Ilya is Independent Consultant on Metrology. He has published above 200 papers on metrology and quality in analytical chemistry. Ilya is a member of the CITAC and ISO/TC 334, Titular member of the IUPAC Analytical Chemistry Division and Chair of the IUPAC Subcommittee on Metrology in Chemistry.