Report of the Second Interlaboratory Comparison Organised by the Community Reference Laboratory for Heavy Metals in Feed and Food: Total Cd, Pb and Hg in Mineral Water
The Institute for Reference Materials and Measurements (IRMM) of the European
Commission's Directorate-General Joint Research Centre holds the Community
Reference Laboratory for Heavy Metals in Feed and Food (CRL-HM). One of the
core tasks is to organise interlaboratory comparisons (ILCs) among appointed
National Reference Laboratories (NRLs). This report presents the results of the
second ILC of the CRL-HM which focused on the determination of the total Cd, Pb
and Hg content in mineral water.
The test material used in this exercise was a commercial mineral water
purchased in Belgium at a local supermarket. The material was spiked with Cd,
Pb and Hg, rebottled and dispatched by the Reference Material Unit of the IRMM.
The samples were dispatched on the first half of May 2007. Each participant
received two sets of samples containing one bottle per set. Each bottle contained
approximately 100 mL of test material. Twenty participants from 17 countries
registered to the exercise of which 20 submitted results for Cd and Pb and 19 for
Hg.
The assigned values were those obtained from the gravimetric measurements
used to spike the material. The homogeneity and stability studies were
subcontracted to the University of Natural Resources and Applied Life Sciences
(BOKU) in Vienna.
The uncertainty of the assigned values was calculated combining the uncertainty
of the spiking procedure with a contribution for the between-bottle homogeneity
and for long-term stability of the test material. Participants were invited to report
the uncertainty on their measurements. This was done by all them.
Laboratory results were rated with z and zeta scores in accordance with ISO
135281. Standard deviation for proficiency assessment (also called target
standard deviation) for Cd, Pb and Hg was 10% of the assigned value.JRC.D.4-Isotope measurement