7. Quantity of material

The main objective of analytical chemistry is to determine qualitatively and/or quantitatively the composition of a sample of matter; metrology in chemistry essentially aims to measure a "quantity of matter", a quantity used to characterize a number of entities. The case of metrology in chemistry differs from that of physical quantities, however, in that the introduction of traceability concepts is relatively recent. It was only in 1993 that the CIPM set up the Consultative Committee for Amount of Substance (CCQM) –, which deals specifically with chemical metrology –, at a time when analysts and users of chemical measurements were increasingly confronted with the lack of comparability of results, which sometimes differed by one or more orders of magnitude, as in ultra-trace analysis.

Four subfields, corresponding to the classical disciplines of chemistry, were initially...