This comparison serves to demonstrate the capabilities of IPQ, INMETRO and NMISA in the production of primary gas mixtures of automotive emission in nitrogen.
NMI-VSL will analyze the gas mixtures to be gravimetrically produced and analyzed by the three other participants.
The pressure in the cylinders will be approximately 100 bar; cylinders of 5 dm3 nominal will be used. Each cylinder will have its own reference value calculated from the gravimetric preparation.
Participating laboratories are requested to specify in detail the calculation of the gravimetric composition including purity estimation and how the evaluation of uncertainty was performed.
Transport of the cylinders to VSL will be arranged and paid for by participants. VSL will arrange and pay for return shipment of the cylinders.
Final Report 2011-09-12
The comparison has been completed and the results are available in the KCDB.
The results in summary:
The capabilities for the preparation of certified reference materials of carbon monoxide, carbon dioxide, and propane in nitrogen have been compared. The participating national metrology institutes submitted each a gravimetrically prepared gas mixture of a specified target composition typical for the automotive industry to the coordinating laboratory. All mixtures were analysed by the coordinating laboratory using a gas chromatograph equipped with a thermal conductivity detector in three runs under repeatability conditions. Based on the calibration curve, reference values were assigned to the amount fractions of carbon monoxide, carbon dioxide, and propane. The degrees–of–equivalence were established as difference between the gas composition as calculated from preparation and the measured one, and its associated uncertainty. All participants obtained satisfactory results.