Guidelines for CITAC projects and CITAC procedure for support of conferences and workshops

News and Announcements

Guidelines for CITAC projects and CITAC procedure for support of conferences and workshops     

CITAC: Cooperation on international traceability in analytical chemistry

Chronicle

CITAC: Cooperation on international traceability in analytical chemistry     

CITAC Award 2010: Three Most Interesting Papers in Metrology in Chemistry

News and Announcements

CITAC Award 2010: Three Most Interesting Papers in Metrology in Chemistry     

CITAC Award 2009: the three most interesting papers in Metrology in Chemistry

News and Announcements

CITAC Award 2009: the three most interesting papers in Metrology in Chemistry     

Disseminating traceability in chemical measurement: Principles of a new EURACHEM/CITAC guide

Accreditation and Quality Assurance -     

CITAC Symposium: Quality of Measurements in Analytical Chemistry, 3rd September 2001, Athens,Greece

Accreditation and Quality Assurance -     

Uncertainty from sampling in measurements of aflatoxins in animal feedingstuffs: application of the Eurachem/CITAC guidelines

The duplicate method for estimating uncertainty from measurement including sampling is presented in the Eurachem/CITAC guide. The applicability of this method as a tool for verifying sampling plans for mycotoxins was assessed in three case studies with aflatoxin B(1) in animal feedingstuffs. Aspects considered included strategies for obtaining samples from contaminated lots, assumptions about distributions, approaches for statistical analysis, log(10)-transformation of test data and applicability of uncertainty estimates. The results showed that when duplicate aggregate samples are formed by interpenetrating sampling, repeated measurements from a lot can be assumed to approximately follow a normal or lognormal distribution. Due to the large variation in toxin concentration between sampling targets and sometimes very large uncertainty arising from sampling and sample preparation (U(rel) ≥ 50%), estimation of uncertainty from log(10)-transformed data was found to be a more generally applicable approach than application of robust ANOVA.     

About acceptance and rejection zones as defined in the EURACHEM/CITAC Guide (2007) “Use of uncertainty information in compliance assessment”

Considering measurement uncertainty is mandatory in assessing conformance to legal or compositional limits, and specific guidelines are available issued by ASME, ISO and Eurachem/CITAC. However, differences between ISO and EURACHEM/CITAC wordings could induce some perplexities in the most careful readers. Possible problems arise from considering that, before performing a test, it should be decided whether it is to be a test for conformity or a test for non-conformity. This choice could perhaps require some renaming of acceptance/rejection zones as defined in the EURACHEM/CITAC Guide. A tentative solution is discussed in this contribution.