Analysis of Coated Drug Beads Using Time of Flight Secondary Ion Mass Spectroscopy (ToFSIMS )

Topics Covered

Background
     X-Ray Photoelectron Spectroscopy (XPS)
Time of Flight Secondary Ion Mass Spectroscopy (ToF-SIMS)
Case Study: Time of Flight Secondary Ion Mass Spectometry Imaging of Coated Drug Beads

Background

Modern methods of surface chemical characterisation play an important role in the study and development of pharmaceutical products. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) are two of the most important surface analysis techniques, with the following features:

X-Ray Photoelectron Spectroscopy (XPS)

  • Elemental and chemical state information.
  • Quantitative analysis.

Time of Flight Secondary Ion Mass Spectroscopy (ToF-SIMS)

  • Detailed and highly specific chemical information (elements, chemical groups, polymer structures, molecules).
  • Highly sensitive (trace detection limits).
  • Imaging with high spatial resolution (< 200 nanometres).

Case Study: Time of Flight Secondary Ion Mass Spectometry Imaging of Coated Drug Beads

State-of-the-art Time of Flight Secondary Ion Mass Spectroscopy has now become an important analytical tool for the research and development of controlled-release drug delivery systems.  One approach is to encapsulate a drug bead within a multi-layer polymer coating where the properties of the latter control the rate of drug release.

Since the production of this type of multi-component system is difficult, analysis of the final product is vital.  As a mass spectrometry, Time of Flight Secondary Ion Mass Spectroscopy is ideally suited for this task and can provide an assessment of the thickness and uniformity of the coating layers as well as the distribution of the drug and other excipients within the bead.  This is illustrated by the Time of Flight Secondary Ion Mass Spectroscopy images below for a drug used in heart medication, where the beads were cross-sectioned to facilitate the analysis (data courtesy of Physical Electronics, Eden Prairie, USA).

Figure 1. Optical micrograph of a controlled drug delivery bead.

Figure 2. RGB overlay of Time of Flight Secondary ion Mass Spectroscopy images.

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