Magnesium stearate surface coverage on tablets and drug crystals: Insights from SEM-EDS elemental mapping

Chamara A. Gunawardana, Angela Kong, Daniel O. Blackwood, C. Travis Powell, Joseph F. Krzyzaniak, Myles C. Thomas, Changquan Calvin Sun

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


Scanning electron microscopy-based energy dispersive X-ray spectroscopy (SEM-EDS) is proposed as a versatile tool for quantifying surface area coverage (SAC) by magnesium stearate (MgSt) on pharmaceutical tablets and particles. Our approach involved fast elemental mapping and subsequent SAC quantitation by image analysis. The study was conducted using a multi-component system, but the particle-level mapping was limited to active pharmaceutical ingredient (API) crystals. For both tablets and API particles, the calculated SAC against MgSt loading afforded a positive linear correlation over the range of MgSt levels examined in this work. On the tablet surface, MgSt was found to be preferentially concentrated at or in the close vicinity of grain boundaries, supporting the idea of compression-driven migration and relocation of MgSt within the tablet. On the particle surface, only discrete aggregates of MgSt were observed, as opposed to the widely accepted phenomenon of the formation of a thin lubricant film around host particles. The selection of proper SEM-EDS operating conditions and the challenges confronted in particle surface mapping are discussed in detail.

Original languageEnglish (US)
Article number122422
Pages (from-to)122422
JournalInternational journal of pharmaceutics
StatePublished - Jan 5 2023

Bibliographical note

Funding Information:
This work was supported by a grant from Pfizer Inc. Parts of this work were carried out in the Characterization Facility, University of Minnesota, which receives partial support from the NSF through the MRSEC (Award Number DMR-2011401) and the NNCI (Award Number ECCS-2025124) programs.

Publisher Copyright:
© 2022 Elsevier B.V.


  • Chemical imaging
  • Elemental mapping
  • Magnesium stearate
  • energy dispersive X-ray spectroscopy (EDS)
  • scanning electron microscopy (SEM)
  • surface area coverage (SAC)

MRSEC Support

  • Shared

PubMed: MeSH publication types

  • Journal Article


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