title: Data requirements for the reliable use of atomic pair distribution functions in amorphous pharmaceutical fingerprinting.
abstract: OBJECTIVE
  To determine the optimal measurement strategy for fingerprinting condensed phases of pharmaceutical systems using atomic pair distribution functions (PDFs) obtained from data collected using several types of x-ray diffraction instruments.
  
  
  METHODS
  PDFs of crystalline and amorphous-phase molecular systems derived from data accessible to copper-, molybdenum-, and silver-anode laboratory sources were compared to one another and synchrotron data using qualitative and quantitative methods.
  
  
  RESULTS
  We find that reliable fingerprinting is still possible using silver and molybdenum laboratory sources, but data from copper anode laboratory sources are unreliable for fingerprinting, yielding ambiguous and potentially incorrect results.
  
  
  CONCLUSIONS
  The ambiguities make data measured using low energy x-rays unsuitable for fingerprinting active pharmaceutical ingredients and small molecule systems, and, in general, copper anode diffractometers are undesirable for this purpose; however, laboratory x-ray sources with either Mo or Ag anodes are well suited for this application.
authors.affiliation: Department of Applied Physics and Applied Mathematics, Columbia University, 500 W. 120th St., Room 200 Mudd, MC 4701, New York, New York 10027, USA. td2218@columbia.edu
authors.forename: Timur
authors.initials: T
authors.lastname: Dykhne
authors.forename: Ryan
authors.initials: R
authors.lastname: Taylor
authors.forename: Alastair
authors.initials: A
authors.lastname: Florence
authors.forename: Simon J L
authors.initials: SJ
authors.lastname: Billinge
mesh_terms: D000465:Algorithms; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000737:chemistry; D000927:Anticonvulsants / Q000737:chemistry; D002220:Carbamazepine / Q000737:chemistry; D003460:Crystallization; D007213:Indomethacin / Q000737:chemistry; D004364:Pharmaceutical Preparations / Q000737:chemistry*; D014961:X-Ray Diffraction / Q000379:methods*
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D000927:Anticonvulsants; D004364:Pharmaceutical Preparations; D002220:Carbamazepine; D007213:Indomethacin