Feature articles
Pesticides
Analytical chemistry - metrology in chemistry in particular - is currently undergoing major developments as a result of high demand from society for measurement of chemical compounds in the environment, health and agri-food sectors. In each of these fields, along with other industrial sectors, thousands of laboratories carry out millions of analyses every year. The metrological traceability of these measurements is not always adequately ensured in sensitive sectors such as environment and health. Pesticides are a prime example of a field where metrology in chemistry can play a significant role. The level of water pollution caused by these compounds is alarmingly high and numerous laboratories are analysing pesticides on a daily basis. Unfortunately, despite the implementation of sophisticated analysis techniques, traceability to the SI system is not always proved. This document covers the question of pesticides in general and reviews the analytical and metrological aspects.
Pesticides (pdf - 407 kB)
Chip-scaled atomic clocks
The Bose-Einstein Condensate, a new state of matter predicted in 1924 by A. Einstein then experimentally observed in 1995 by E.A. Cornell and C.E. Wieman on the one hand and W. Ketterle on the other hand, has aroused great interest from the scientific community. And Metrology was not lagging behind. As the LNE-SYRTE, the national metrology laboratory designated under the French metrology scheme to carry out the time and frequency activities, had embarked in a project based on the Bose-Einstein condensates, in collaboration with the Laboratory Kastler Brossel and the Ecole Normale Supérieure of Paris. The aim was to realize a chip-scaled atomic clock that will operate alternatively with the thermal atomic and degenerated gases.
Chip-scaled atomic clocks (pdf - 748 kB)
Balance du watt
The kilogram is the unique unit among the International System (SI) that is still defined from a single artefact, in accordance with the definition that was adopted by the General Conference on Weights and Measures (CGPM) in 1889. It is equal to the mass of the international prototype kilogram, platinum-iridium material standard, kept by the International Bureau of Weights and Measures (BIPM), and named 
.
However, even if represents the mass unit by definition, the international prototype is not perfectly stable, owing to its interaction with the surrounding medium.
Encouraged by the 20th and 21th CGPM (1995-resolution 5 and 1999-resolution 7) and to contribute to the international effort, France has made the decision to realize an experiment called "Watt Balance" based on a principle devised in 1976 by B.P. Kibble (NPL).
It has a twofold objective :
- Determine the stability of the mass unit by reference to a quantity supposed to be invariant such as the Planck’s constant (h),
- Determine the units of the International System according to the value of that same constant.
If this determination can be carried out with a sufficiently low uncertainty, satisfying both objectives could allow obtaining an evolution in the definition of the mass unit based on a fundamental constant, as was the case for the metre in 1983 by setting the value of the light speed conventionally, and hence relate the metre to the second.
