title: Application of 14N NQR to the study of piroxicam polymorphism.
abstract: A study was conducted to test the capability of the (14)N nuclear quadrupole resonance (NQR) method to discriminate qualitatively and quantitatively among different forms of piroxicam. Samples of commercial piroxicam form I and its monohydrate were obtained on the local market. Additionally, samples of form I and II were prepared by recrystallization in 1,2-dichloroethane and ethanol, respectively. DSC and FT-IR were employed as reference methods. A (14)N NQR spectrometer was used to measure samples of different forms and mixtures of piroxicam at 2587 and 3439  kHz. DSC and FT-IR clearly confirmed differences between the different piroxicam forms. Measurements of (14)N NQR signals of different forms of piroxicam at 2587  kHz detected only spectral peaks of form I. The dependence of (14)N NQR signal intensity on the concentration of form I in mixtures with the monohydrate showed a clear linear relationship at both measured frequencies, though the scattering of data was greater at 3439  kHz due to the lower S/N ratio. The (14)N NQR method has the potential to become an additional and important spectroscopic tool in the study of solid-state forms, not only of pure active pharmaceutical ingredients or excipients, but also of their mixtures. This ability lends the method to a possible successful utilization at different levels of pharmaceutical manufacturing and product quality control.
authors.affiliation: Faculty of Pharmacy, University of Ljubljana, Aškerčeva 7, SI-1000 Ljubljana, Slovenia.
authors.forename: Zoran
authors.initials: Z
authors.lastname: Lavrič
authors.forename: Janez
authors.initials: J
authors.lastname: Pirnat
authors.forename: Janko
authors.initials: J
authors.lastname: Lužnik
authors.forename: Janez
authors.initials: J
authors.lastname: Seliger
authors.forename: Veselko
authors.initials: V
authors.lastname: Zagar
authors.forename: Zvonko
authors.initials: Z
authors.lastname: Trontelj
authors.forename: Stane
authors.initials: S
authors.lastname: Srčič
mesh_terms: D002152:Calorimetry, Differential Scanning; D003460:Crystallization; D000431:Ethanol / Q000737:chemistry; D005025:Ethylene Dichlorides / Q000737:chemistry; D005079:Excipients / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D015394:Molecular Structure; D009584:Nitrogen / Q000737:chemistry; D010894:Piroxicam / Q000737:chemistry*; D011789:Quantum Theory; D011846:Radio Waves / Q000009:adverse effects; D012997:Solvents / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D013057:Spectrum Analysis / Q000379:methods*; D013696:Temperature; D014732:Vibration
chemical_list: D005025:Ethylene Dichlorides; D005079:Excipients; D012997:Solvents; D010894:Piroxicam; D000431:Ethanol; C024565:ethylene dichloride; D009584:Nitrogen