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Polymorph identification in API samples by Solid-state ¹³C NMR

Polymorphism in crystalline solids is defined as substance with the same chemical composition but different lattice structures and/or different molecular conformations. Polymorphs are different crystalline forms of a substance (APIs) that may have different physicochemical properties, bio-availabilities and activities. When formulating a drug product, physico-chemical stability, solubility and bio-availability of active pharmaceutical ingredient (API) is an important aspect. ssNMR spectroscopy can be employed to investigate polymorphism in API’s by probing the environments of nuclei (¹H, ¹³C, ¹⁵N, ¹⁹F, ³¹P etc.) in the solid state and the changes in chemical shift values are often be connected to the changes in conformation or chemical environment of the compound.