The CCQM-K35 key comparison was organized by the Inorganic Analysis Working Group (IAWG) of the CCQM to test the capabilities of national metrological institutes (NMIs) to measure the sulfur content of diesel fuel at the 40 µg/g level. Four NMIs participated in the key comparison: the Federal Institute for Materials Research and Testing (BAM), the Institute for Reference Materials and Measurements (IRMM), the Laboratory of the Government Chemist (LGC) and the National Institute of Standards and Technology (NIST). NIST designed and coordinated the study. All four laboratories used isotope dilution mass spectrometric techniques, but two laboratories (BAM and NIST) used thermal ionization mass spectrometry (TIMS) and two laboratories (IRMM and LGC) used inductively coupled plasma mass spectrometry (ICP-MS). Both techniques require spiking and combustion of the sample prior to the instrumental determination to quantify the amount of sulfur in the fuels. The agreement among the laboratories was good as evidenced by the small values for both the equivalence statements (D_i < 1 µg/g) and the associated uncertainties (u_i < 2.3 µg/g).

A pilot study (P26.1) was performed concurrently on a kerosene sample at the 8 µg/g level and on the same diesel sample used in this K35 study by laboratories preferring to participate in the pilot study. The results of the pilot study are reported separately.

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).