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Evaluation of laboratory performance in IMEP water interlaboratory comparisons

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Abstract

The aim of International Evaluation Programme (IMEP) is to present objectively the quality of chemical measurements. Participants in IMEP compare their reported measurement results with independent external certified reference values with demonstrated traceability and uncertainty, as evaluated according to international guidelines. Three major interlaboratory comparisons (ILCs), IMEP-6, IMEP-9 and IMEP-12, on trace elements in water were carried out from 1994 to 2000. Participants' results for Cd, Fe and Pb concentrations from these three different IMEP water ILCs were compared by means of suitable performance indicators. The performance evaluation criteria were set according to the requirements stated in the Council Directive 98/83/EC of 3 November 1998 on the quality of water intended for human consumption. Two different performance indicators were selected for evaluation of the individual participants' results: the commonly used z-score and the not so well-known E n number. The group performance indicator is based on the variation of z-scores. To assess the individual measurement performance, not only the deviation of the reported measurement values from the certified reference value, but also criteria for maximum and minimum acceptable uncertainties were taken into account. The participants' performance is also reviewed by means of using a simple graphical tool, called “Naji-plots”.

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Authors and Affiliations

  1. Czech Accreditation Institute, Prague, Czech Republic

    Martina Bednarova

  2. European Commission, Joint Research Centre, Institute for Reference Materials and Measurements, BE-2440, Geel, Belgium

    Yetunde Aregbe, Caroline Harper & Philip D. P. Taylor

Authors
  1. Martina Bednarova
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  2. Yetunde Aregbe
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  3. Caroline Harper
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  4. Philip D. P. Taylor
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Correspondence to Yetunde Aregbe.

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Bednarova, M., Aregbe, Y., Harper, C. et al. Evaluation of laboratory performance in IMEP water interlaboratory comparisons. Accred Qual Assur 10, 617–626 (2006). https://doi.org/10.1007/s00769-005-0031-6

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  • DOI: https://doi.org/10.1007/s00769-005-0031-6

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