A Key Comparison (CCQM-K31) of the determination of arsenic in a marine shellfish (oyster tissue) was conducted under the auspices of the CCQM Inorganic Analysis Working Group as a follow-up to the CCQM-P11 Pilot Study. Arsenic was present at naturally occurring levels, and in naturally occurring (non-spiked) forms in this material. Six national metrology institutes (NMIs) and one unofficial participant submitted data for this study using a variety of analytical methods. One lab appeared to have analytical problems and asked that their results be excluded from the Key Comparison Reference Value (KCRV). The remaining five reported arsenic results from official participants fell into a range of 11% (relative, compared to the mean) with a relative standard deviation of 4.4%. The observed results were considerably worse than those from the Pilot Study, even though the matrix and analyte levels were nearly identical. Excluding the results from one apparently outlying lab in CCQM-P11, the observed range of data from ten labs was 5.4% (relative, compared to the mean) with a relative standard deviation of 1.7%.

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).