Quantification of surface composition and surface structure of inhalation powders using TOF-SIMS

Area of Science:

• Materials Science
• Analytical Chemistry
• Pharmaceutical Sciences

Background:

• Surface properties significantly influence powder formulation behavior, especially for dry powders for inhalation.
• These properties dictate inter-particulate forces, directly affecting the dispersibility of pharmaceutical formulations.
• Understanding surface composition is key to optimizing powder performance.

Purpose of the Study:

• To develop and apply a multivariate time-of-flight secondary ion mass spectrometry (TOF-SIMS) methodology.
• To quantify the surface composition and chemical distribution in various dry powder blends.
• To gain detailed insight into the surface structure of pharmaceutical powder formulations.

Main Methods:

• Development of a multivariate TOF-SIMS approach for surface analysis.
• Utilizing non-negatively constrained alternating least squares to fit mass spectra.
• Calculating average surface coverage and image features from pixel compositions.
• Analysis of binary blends (lactose/coating agents) and drug-carrier blends.

Main Results:

• Successful quantification of surface composition and chemical distribution in dry powder blends.
• Detailed insights into the surface composition and structure of model and relevant pharmaceutical systems.
• Demonstration of TOF-SIMS capability in characterizing complex powder surfaces.
• Comparison of TOF-SIMS results with X-ray photoelectron spectroscopy (XPS) for validation.

Conclusions:

• The developed multivariate TOF-SIMS methodology is effective for characterizing the surface of dry powder blends.
• This technique provides valuable information for optimizing powder formulations, particularly for inhalation applications.
• TOF-SIMS offers a powerful tool for detailed surface analysis in pharmaceutical science.