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In Germany a system of primary amount of substance standards for elemental analysis is being developed, which forms the material's basis for the National Standards for element determination. The metrological concept and technical approach is briefly described. The objective of traceability in chemistry, in this case for elemental determination, is illustrated on the example of copper.

The metrological principles of neutron activation analysis are discussed. It has been demonstrated that this method can provide elemental amount of substance with values fully traceable to the SI. The method has been used by several laboratories worldwide in a number of CCQM key comparisons – interlaboratory comparison tests at the highest metrological level – supplying results equivalent to values from other methods for elemental or isotopic analysis in complex samples without the need to perform chemical destruction and dissolution of these samples. The CCQM accepted therefore in April 2007 the claim that neutron activation analysis should have the similar status as the methods originally listed by the CCQM as 'primary methods of measurement'. Analytical characteristics and scope of application are given.

In the wake of the redefinition of the kilogram, the last unit of the International System of Units (SI) that is still based on a man-made artefact, discussions were launched on the necessity of redefining other units, amongst other the unit mole. Since 1971 the mole is defined as the amount of substance of a system that contains as many elementary entities as there are atoms in 0.012 kilogram of carbon 12. The symbol of the unit is 'mol'. When the mole is used, the elementary entities must be specified and may be atoms, molecules, ions, electrons, other particles, or specified groups of such particles. The definition is based on the pre-existing choice to set the relative atomic mass of carbon 12 equal to 12 exactly. In the proposed new definition the mole is the amount of substance containing exactly 6.022 141 79 × 1023 atoms or molecules, ions, electrons, other particles, or specified groups of such particles, i.e. the Avogardo constant would have a fixed value without an uncertainty. This contribution critically examines the submitted arguments to justify the proposed redefinition of the unit mole by 2011 for their persuasive power to change a scientific and cultural good such as a unit of measurement. As shown, there are no convincing scientific arguments for a redefinition of the mole that stand a closer examination. The current definition is well understood, established in science and technology for almost 50 years and is still up to date.

In clinical chemistry and medical diagnostics, the reliability of the results obtained by numerous testing protocols has a major impact on the critical decision-making processes. Considerable efforts are made by international institutes to promote and give guidance on measurement comparisons and metrological traceability using appropriate certified reference materials. The concentration values or amount of substance contents are usually assigned to chemical analytical results. In contrast, the most relevant quantity is the activity of ions in clinical chemistry. Activity corresponds to the available biologically active part of these components in a mixture. Many measurement methods and instruments currently in use do not differentiate between the total substance concentration and its biologically active component. In physiological solutions, such as blood plasma, the chemical activity makes a clear difference between ion or substrate concentration. Ion selective electrodes (ISE) are widely used to directly measure the activity of ions. Measurement by means of ion-selective electrodes is a standard method in point of care testing units (POCT) for continuous monitoring for e.g. haemodialysis, cardiac surgery and in intensive care units. A metrological approach to ISE potentiometric measurements is proposed, to determine the activity with their uncertainty. A prerequisite is to develop an activity calibration scale for complex electrolyte solutions with known and traceable ion activities.