Calibration devices

Development of calibration devices

For a reliable and accurate measurement of target molecule concentrations, it is necessary to calibrate the instruments beforehand. Therefore, a calibration source, either internal or external to the instrument, is needed. For liquid-phase analysis, dilute solutions of compounds can be obtained from certified standard commercial solutions by simple dilution in the appropriate solvent. For gas-phase analyses, gas mixtures exist for certain species, particularly the most volatile. However, these gas cylinders are rarely easy to transport as they are cumbersome. The aim here is to develop more compact and less gas-consuming devices for the generation of VOCs and SVOCs mixtures at perfectly controlled and reproducible concentrations.

For example, a compound can be generated in the gaseous phase by a permeation placed in a controlled-temperature enclosure supplied by a constant flow of nitrogen. . After a certain stabilisation time, the concentration obtained is stable over time. This concentration depends mostly on the emission rate of the permeation tube used, which is expressed in ng h-1. Several permeation tubes should be used to generate a gaseous mixture of several compounds.

Studies and developments are being carried out here to :

  • Reduce the time required to stabilise the concentration of the compound(s) in the gas phase;
  • Predict the concentration generated based on abacuses and the experimental conditions used;
  • Improve the stability of the concentrations generated;
  • Improve the reproducibility of the concentrations generated;
  • Improve the portability of the device by reducing its size and weight;
  • Reduce manufacturing costs.

Other alternatives to the permeation tube may also be considered.

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