Necessity of Establishing Chemical Integrity of Polymorphs of Drug Substance Using a Combination of NMR, HPLC, Elemental Analysis, and Solid-State Characterization Techniques: Case Studies

Polymorphism is a solid-state phenomenon; hence, solid-state techniques such as XRPD, DSC, and FT-IR are used for characterization. Many a time, only XRPD is used. These techniques ignore the most important aspects, i.e., chemical purity and the chemical integrity of the polymorph, which can be confirmed by techniques such as 1 H NMR, HPLC, and elemental analysis. The aim of this article is to emphasize how techniques such as 1 H NMR, elemental analysis, and HPLC purity in addition to other solid-state characterization techniques would help to prove that the drug really exists in different polymorphic forms. H 1 NMR, HPLC, and elemental analysis reveal the formation of different compounds and not polymorphs in the case of pioglitazone·HCl and glyburide. In the cases of irbesartan and ropinirole·HCl use of a single solid-state characterization technique such as XRPD is not enough for establishing the existence of different polymorphic forms.