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International Centre for Diffraction Data round robin on quantitative Rietveld phase analysis of pharmaceuticals

  • T. G. Fawcett (a1), F. Needham (a1), J. Faber (a1) and C. E. Crowder (a1)


The ICDD sponsored a round robin on the quantitative Rietveld phase analysis of pharmaceuticals. 11 participating laboratories from the pharmaceutical community submitted both raw data and processed quantitative results. The purpose of the round robin was to evaluate current practices in laboratories, so procedures and methods were not specified, but they were recorded. Cluster analysis tools were applied to all the data sets and their use helped identify the root causes of several types of errors in specimen preparation, data treatment, and Rietveld analysis. The authors considered this round robin to be difficult. Sample homogeneity was an issue and molecular orientation was observed in many data sets. Each material studied has structural polymorphs so the selection of starting parameters and their refinement was nontrivial. Similar to prior round robins on inorganic materials and minerals, this round robin identified operator errors as the major contributor to poor results. Four laboratories achieved excellent results on all phases in all three samples, with accuracy within relative errors of 5% to 10%.


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Powder Diffraction
  • ISSN: 0885-7156
  • EISSN: 1945-7413
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