Crystal Quality and Physical Reactivity in the Case of Flufenamic Acid (FFA)

In reality, no crystal is perfect. Crystals bear defects both in the bulk and on the surface. The purpose of this project is to study the correlation between crystal defect density and reactivity of physical transformation. The hypothesis is that larger crystals have the opportunity to pick up more defects during crystal growth than smaller crystals, therefore, have higher reactivity. Flufenamic acid (FFA) was used as a model compound. Phase transformation of crystal Form I (white) to Form III (yellow) of FFA was studied, and observed that larger crystals of FFA Form I transform faster. Furthermore, the etching pits identified on the major crystal faces (1 0 0) using atomic form microscopy (AFM) also showed that larger crystals had higher surface defect density than smaller ones, which correlates with the finding that larger crystals transforms faster than smaller ones. © 2010 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99:3839–3848, 2010