Volume 37, Issue 2 (March 2009)
Indentation Measurements on Compacted Pharmaceutical Powders: Establishing the Sources of Variation in White Light Interferometer Dent Measurements
Indentation measurements are commonly used to determine the mechanical properties of pharmaceutical compacts. Specifically, they are used to assess their resistance to plastic deformation and to help predict tablet properties. To date there has been little research reported aimed at understanding the variation associated with these types of measurements. In this work experiments were conducted to identify and, where possible, quantify the sources of variation for dent measurements on pharmaceutical excipient compacts using a white light interferometer. Statistical analyses of the results revealed that operator-to-operator and sample-to-sample variability each accounted for approximately 2.5 % of the total variability, whereas the intrinsic error of the experimental test procedure was about 10 % of the total variability. The remaining variability was due to known differences in the material properties or test conditions. The capability of the dent dimension measurements was determined to be approximately 8 % of the mean value, and thus it was possible to quantify the discriminating power of this type of compact mechanical property measurement.