TY  - JOUR
A1  - Scheidel, Sebastian
A1  - Östreicher, Laurina
A1  - Mark, Isabelle
A1  - Pöppler, Ann-Christin
T1  - You cannot fight the pressure: Structural rearrangements of active pharmaceutical ingredients under magic angle spinning
JF  - Magnetic Resonance in Chemistry
N2  - Although solid-state nuclear magnetic resonance (NMR) is a versatile analytical tool to study polymorphs and phase transitions of pharmaceutical molecules and products, this work summarizes examples of spontaneous and unexpected (and unwanted) structural rearrangements and phase transitions (amorphous-to-crystalline and crystalline-to-crystalline) under magic angle spinning (MAS) conditions, some of them clearly being due to the pressure experienced by the samples. It is widely known that such changes can often be detected by X-ray powder diffraction (XRPD); here, the capability of solid-state NMR experiments with a special focus on \(^{1}\)H-\(^{13}\)C frequency-switched Lee–Goldburg heteronuclear correlation (FSLG HETCOR)/MAS NMR experiments to detect even subtle changes on a molecular level not observable by conventional 1D NMR experiments or XRPD is presented. Furthermore, it is shown that a polymorphic impurity combined with MAS can induce a crystalline-to-crystalline phase transition. This showcases that solid-state NMR is not always noninvasive and such changes upon MAS should be considered in particular when compounds are studied over longer time spans.
KW  - \(^{1}\)H-\(^{13}\)C HETCOR
KW  - API
KW  - structural changes
KW  - XRPD
KW  - solid-state NMR
KW  - MAS
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-318838
VL  - 60
IS  - 6
SP  - 572
EP  - 582
ER  -