Polymorphic discrimination using atomic force microscopy: Distinguishing between two polymorphs of the drug cimetidine

The polymorphism of cimetidine in tablet (A) and suspension (B) forms was studied using an alternative method of utilizing atomic force microscopy. The method was based on phase imaging and amplitude-phase distance (a-p,d) measurement. Form A has a larger attractive region compared to form B, significant part of which is shown to be due to attractive capillary forces. However, it is important to note that other polymorphic systems need to be investigated to evaluate the usefulness of the proposed technique as a generic means of polymorphic characterization.