Spectroscopic and X-ray diffraction study of structural disorder in cryomilled and amorphous Griseofulvin

Anna Zarów, B. O. Zhou, Xianqin Wang, Rodolfo Pinal, Zafar Iqbal

Research output: Contribution to journalArticlepeer-review

23 Scopus citations

Abstract

Structural disorder induced by cryogenic milling and by heating to the amorphous phase in the active pharmaceutical ingredient Griseofulvin has been studied using Raman spectroscopy, X-ray powder diffraction (XRPD), and fluorescence spectroscopy. A broad, exciting-frequencyindependent scattering background in the Raman spectra and changes in intensities and splitting of some of the Raman lines due to lattice and molecular modes have been observed. In the cryomilled samples this strong background is deconvoluted into two components: one due to lattice disorder induced by cryomilling and the other due to Mie scattering from nanosized crystallites. A single-component background scattering attributed to lattice disorder is seen in the Raman spectrum of the amorphous sample. Fluorescence measurements showed an intrinsic fluorescence signal in as-received Griseofulvin that does not correspond to the inelastic background in the Raman spectra and, moreover, decreases in intensity upon cryomilling, thus excluding an assignment of the Raman background intensity to impurity- or molecular-defect-induced fluorescence. Wide-angle XRPD measurements on cryomilled Griseofulvin shows a broad two-component background consistent with the backgroundscattering component in the Raman data associated with lattice disorder, but at longer correlation lengths. Persistence of this disorder to even longer lengths is evident in small-angle synchrotron XRPD data on micronized Griseofulvin taken as a function of temperature from the crystalline to the amorphous phase.

Original languageEnglish (US)
Pages (from-to)135-143
Number of pages9
JournalApplied Spectroscopy
Volume65
Issue number2
DOIs
StatePublished - Feb 2011

All Science Journal Classification (ASJC) codes

  • Instrumentation
  • Spectroscopy

Keywords

  • API
  • Active pharmaceutical ingredient
  • Amorphous phase
  • Cryomilling
  • Crystalline defects
  • Disorder
  • Fluorescence spectroscopy
  • Griseofulvin
  • Lattice disorder
  • Milling
  • Raman spectroscopy
  • X-ray powder diffraction
  • XRPD

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