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The Homogeneity study

15/05/2021,


Extract from the international harmonized protocol for the proficiency testing of (chemical) analytical laboratories (2006)

by Thompson M, Ellison WLR, Wood R, (IUPAC technical report); https://doi.org/10.1351/pac200678010145


A recommended procedure for testing a material for sufficient homogeneity

The procedure to be followed by the Laboratory preparing proficiency test materials is as follows:

  • Prepare the whole of the bulk material in a form that is thought to be homogeneous, by an appropriate method. Divide the material into the containers that will be used for dispatch to the participants.
  • Select a minimum (n) of 10 containers strictly at random.
  • Separately homogenise the contents of each of the n selected containers and take two test portions. Analyse the 20 test portions in a random order under repeatability conditions by an appropriate method. The analytical methcd used must be sufficiently precise to allow a satisfactory estimation of Ss.
  • Form an estimate (Ss^2) of the analytical variance by one-way analysis of variance (ANOVA), without exclusion of outliers.
  • Report values of mean value, Ss, Sa, n and the result of the F-test
  • If S_pt  is the target value for standard deviation for the proficiency test at analyte concentration, the value of Ss/S_pt should be less than 0.3 for sufficient hanogeneity.


For more information:

  • ISO 17043:2010 - Conformity assessment — General requirements for proficiency testing
  • ISO 13528:2015 - Statistical methods for use in proficiency testing by interlaboratory comparison


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The information above is provided "as is" without warranty of any kind, either express or implied, including, but not limited to, fitness for a particular purpose and absence of errors in the application. The entire risk as to the use, quality, and performance of the application is with the user. The owner of these Tools will not be liable for any incidental, consequential, direct or indirect damages including but not limited to the loss of data, loss of profits, or any other financial loss arising from the use or inability to use the application provided.


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Disclaimer: The information above is provided "as is" without warranty of any kind, either express or implied, including, but not limited to, fitness for a particular purpose and absence of errors in the application. The entire risk as to the use, quality, and performance of the application is with the user. The owner of these Tools will not be liable for any incidental, consequential, direct or indirect damages including but not limited to the loss of data, loss of profits, or any other financial loss arising from the use or inability to use the application provided.