Link to the SI via primary direct methods

Major applications of electrochemical techniques at national metrology institutes

“…With such a low instrumental uncertainty, other factors normally limit the achievable uncertainty, mainly those connected to the solution handling, chemical processes in the cell and the homogeneity of the material. These chemical sources usually represent the major contributions [14,130].…”

Fuel Ethanol Quality: Methods of Analysis and Reference Materials

“…The Consultative Committee for Amount of Substance -Metrology in Chemistry (CCQM) has identified several methods with the potential of being a primary method of measurement, which in the field of chemical measurement, such a method is defined by CCQM as "a method having the highest metrological properties, whose operation can be completely described and understood, for which a complete uncertainty statement can be written down in terms of the units of SI (International System of Units)". However, they are as yet very few [55,56], thus, the CRMs are strongly used to guarantee the quality of chemistry measurements.…”