Calculation of effective penetration depth in X-ray diffraction for pharmaceutical solids

Area of Science:

• Materials Science
• Pharmaceutical Science
• Analytical Chemistry

Background:

• Glancing incidence X-ray diffraction (GIXRD) is used for surface phase transformation analysis.
• The Parratt equation, traditionally used for depth profiling, has limitations for pharmaceutical solids.
• Pharmaceutical solids often require analysis at depths of 50-200 micrometers.

Purpose of the Study:

• To develop a more relevant method for defining X-ray penetration depth in pharmaceutical solids.
• To overcome limitations of the Parratt equation for pharmaceutical depth profiling.
• To establish an effective penetration depth definition based on diffractometer signal detection limits.

Main Methods:

• Developed a novel method to define X-ray effective penetration depth.
• Utilized an exponential absorption law for calculating penetration depth.
• Empirically verified the method using bilayer compacts of mannitol and lactose with known thicknesses.

Main Results:

• The proposed method provides a more accurate definition of X-ray penetration depth for pharmaceutical solids.
• The effective penetration depth can be calculated directly from an exponential absorption law for depths of interest.
• Empirical verification confirmed the relevance of the new depth definition.

Conclusions:

• The developed method offers a superior alternative to the Parratt equation for X-ray depth profiling in pharmaceutical applications.
• This approach enhances the analysis of surface phase transformations in pharmaceutical compacts.
• The findings contribute to more precise characterization of pharmaceutical solid materials.