The aim of this comparison was to compare capabilities for the preparation and value assignment of gas mixture standards for benzene, chloroform, dichloromethane, trichloroethylene, tetrachloroethylene, 1,2-dichloroethane, 1,3-butadiene and vinyl chloride in nitrogen (HAPs-8), maintained at national metrology institutes (NMIs). The measurements in this key comparison took place in 2003. There were six participants and one coordinating laboratory. The key comparison reference value (KCRV) was based on the gravimetric preparation for all components. The range of the nominal amount-of-substance fractions of the comparison standard is 90 nmol/mol to 110 nmol/mol. The Chemical Evaluation Research Institute (CERI, Japan) prepared gravimetric mixture samples of HAPs-8 in 10 L aluminium cylinders and the homogeneity and long term stability of these samples were evaluated at CERI before and after the shipment of the cylinders to the participants. Each participating laboratory was shipped one cylinder to be analysed and then returned to the CERI. Each sample was reanalysed to verify whether the contents were stable throughout the comparison. These measurements showed no significant change in the amount fraction within the estimated uncertainty of the measurements except for 1,2-dichroloethane. These deviations were combined into the uncertainty of the comparison samples but were small enough compared to the deviations from values reported by participating laboratories and the gravimetric values of the samples.

Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.

The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).