title: (14) N nuclear quadrupole resonance study of piroxicam: confirmation of new polymorphic form V.
abstract: A new polymorphic crystal form of piroxicam was discovered while preparing crystalline samples of piroxicam for (14) N nuclear quadrupole resonance (NQR) analysis. The new crystal form, designated as V, was prepared by evaporative recrystallization from dichloromethane. Three known polymorphic forms (I, II, and III) were also prepared. Our aim was to apply (14) N NQR to characterize the new polymorphic form of piroxicam and compare the results with those of the other known polymorphic forms. Additional analytical methods used for characterization were X-ray powder diffraction (XRPD), thermal analysis, and vibrational spectroscopy. For the first time, a complete set of nine characteristic (14) N NQR frequencies was found for each prepared polymorph of piroxicam. The consistent set of measured frequencies and calculated characteristic quadrupole parameters found for the new polymorphic form V is a convincing evidence that we are dealing with a new form. The already known piroxicam polymorphic forms were characterized similarly. The XRPD results were in accordance with the conclusions of (14) N NQR analysis. The performed study clearly demonstrates a strong potential of (14) N NQR method to be applied as a highly discriminative spectroscopic analytical tool to characterize polymorphic forms.
authors.affiliation: Faculty of Pharmacy, University of Ljubljana, Ljubljana SI-1000, Slovenia. Electronic address: zoran.lavric@ffa.uni-lj.si.
authors.forename: Zoran
authors.initials: Z
authors.lastname: Lavrič
authors.affiliation: Institute of Mathematics, Physics and Mechanics, Ljubljana SI1000, Slovenia.
authors.forename: Janez
authors.initials: J
authors.lastname: Pirnat
authors.affiliation: Institute of Mathematics, Physics and Mechanics, Ljubljana SI1000, Slovenia.
authors.forename: Janko
authors.initials: J
authors.lastname: Lužnik
authors.affiliation: J. Stefan International Postgraduate School, Ljubljana, and Faculty of Electrical Engineering, University of Ljubljana, Ljubljana, Slovenia.
authors.forename: Uroš
authors.initials: U
authors.lastname: Puc
authors.affiliation: Institute of Mathematics, Physics and Mechanics, Ljubljana SI1000, Slovenia.
authors.forename: Zvonko
authors.initials: Z
authors.lastname: Trontelj
authors.affiliation: Faculty of Pharmacy, University of Ljubljana, Ljubljana SI-1000, Slovenia.
authors.forename: Stane
authors.initials: S
authors.lastname: Srčič
mesh_terms: D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000737:chemistry*; D002152:Calorimetry, Differential Scanning; D003460:Crystallization; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D010894:Piroxicam / Q000737:chemistry*; D033362:Powder Diffraction; D017550:Spectroscopy, Fourier Transform Infrared; D013059:Spectrum Analysis, Raman; D014961:X-Ray Diffraction
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D010894:Piroxicam
keywords: 14N nuclear quadrupole resonance (NQR); FTIR; H-bonds; Raman spectroscopy; X-ray powder diffractometry; calorimetry (DSC); physical characterization; piroxicam; polymorphism; spectroscopy