Analysis of Coating Thickness and Porosity of Functional Particles

Introduction

The internal structure and coating of functional particles directly affects tablet performance; controlled release and taste masking. Optical microscopy can only observe a portion of the cross section, and there is concern that the structure may change due to cutting. X-ray microscopy allows non-destructive observation of the three-dimensional structure and numerical evaluation of porosity and coating thickness.

Non-destructive imaging

Figure 1: Morphological observation

Figure 2: Pore distribution

Figure 3: Thickness distribution

Conclusion

In Figure 1, a core with a diameter of 600 µm and three layers of coating (A: 45 µm, B: 13 µm, C: 8 µm) are determined. Figure 2 displays the three-dimensional distribution of pores. The porosity was calculated as 7.43 vol%. In Figure 3, the color distribution shows that the coating thickness varied in the range of 50 to 80 µm. Thus, X-ray microscopy is useful for nondestructive and quantitative understanding of particle structure, and it can be utilized in formulation design and quality evaluation.