An approach for predicting the true density of powders based on in-die compression data

Ramy N. Elsergany, Gerrit Vreeman, Changquan Calvin Sun

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


Helium pycnometry, a commonly used technique for measuring the true density of powders, is sensitive to the release of volatiles during measurement. This can lead to over-estimated true density, and as such, an accurate method for determining the true density of powders containing volatile components is needed. Here, a method based on in-die compression data obtained with a compaction simulator was assessed. Specifically, the stress transmission coefficient (STC), measured using an instrumented die, was used to predict the in-die Heckel mean yield pressure (Py). A true density was derived by repeatedly performing a Heckel analysis using iteratively estimated true density values until the predicted Py value from the measured STC value is obtained from in-die density - pressure data. This novel method was validated using a set of water-free powders. Using crystalline hydrates, we further showed that the calculated true densities were closer to values calculated from crystal structure than those from helium pycnometry. Hence, this method may be used for determining the true density of powders from their STC values.

Original languageEnglish (US)
Article number122875
JournalInternational journal of pharmaceutics
StatePublished - Apr 25 2023

Bibliographical note

Funding Information:
Funding from the National Science Foundation through grant number IIP- 1919037, AFPE through 2022 Dr. Paul B. Myrdal Memorial Pre-Doctoral Fellowship, and Department of Pharmaceutics, UMN, through David and Marilyn Grant Fellowship in Physical Pharmacy (2022-2023) is gratefully acknowledged for partially supporting G.V.

Publisher Copyright:
© 2023 Elsevier B.V.


  • Helium pycnometry
  • In-die Py
  • Stress transmission coefficient
  • True density
  • Water-containing materials

PubMed: MeSH publication types

  • Journal Article


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