Nuclear Quadrupole Resonance (NQR) : a useful spectroscopic tool in pharmacy for the study of polymorphism

Trontelj, Zvonko (author), Pirnat, Janez (author), Jazbinšek, Vojko (author), Lužnik, Janko (author), Srčič, Stanko (author), Lavrič, Zoran (author), Beguš, Samo (author), Apih, Tomaž (author), Žagar, Veselko (author), Seliger, Janez (author)

Nuclear Quadrupole Resonance (NQR) spectroscopy has been known for 70 years. It is suitable for the study of measured (poly)crystalline chemical compounds containing quadrupole nuclei (nuclei with spin I ≥ 1) where the characteristic NQR frequencies represent the fingerprints of these compounds. In several cases, $^{14}$N NQR can distinguish between the polymorphic crystalline phases of active pharmaceutical ingredients (APIs). In order to further stimulate $^{14}$N NQR studies, we review here several results of API polymorphism studies obtained in Ljubljana laboratories: (a) In sulfanilamide, a clear distinction between three known polymorphs (α, β, γ) was demonstrated. (b) In famotidine, the full spectra of all seven different nitrogen positions were measured; two polymorphs were distinguished. (c) In piroxicam, the $^{14}$N NQR data helped in confirming the new polymorphic form V. (d) The compaction pressure in the tablet production of paracetamol, which is connected with linewidth change, can be used to distinguish between producers of paracetamol. We established that paracetamol in the tablets of six different manufacturers can be identified by $^{14}$N NQR linewidth. (e) Finally, in order to get an extremely sensitive $^{14}$N NQR spectrometer, the optical detection of the $^{14}$N NQR signal is mentioned.

• Language: English
• Keywords: NQR, Nuclear Quadrupole Resonance spectroscopy, $^{14}$N NQR, relaxation, drug polymorphism, crystal polymorphism, X-ray powder diffraction (XRPD), powder mixture quantification, NQR with optically pumped magnetometer
• Work type: Article
• Typology: 1.02 - Review Article
• Organization: FFA - Faculty of Pharmacy; FE - Faculty of Electrical Engineering
• Publication status: Published
• Publication version: Version of Record
• Year: 2020
• Number of pages: 22 str.
• Numbering: Vol. 10, iss. 6, art. 450
• PID: 20.500.12556/RUL-133626
• UDC: 53:543.42
• ISSN on article: 2073-4352
• DOI: 10.3390/cryst10060450
• COBISS.SI-ID: 17705475
• Publication date in RUL: 06.12.2021

Record is a part of a journal

• Title: Crystals
• Shortened title: Crystals
• Publisher: MDPI
• ISSN: 2073-4352
• COBISS.SI-ID: 36677893

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• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.
• Licensing start date: 01.06.2020