title: The use of inverse phase gas chromatography to measure the surface energy of crystalline, amorphous, and recently milled lactose.
abstract: OBJECTIVE
  To assess differences in surface energy due to processing induced disorder and to understand whether the disorder dominated the surfaces of particles.
  
  
  METHODS
  Inverse gas chromatography was used to compare the surface energies of crystalline, amorphous, and ball milled lactose.
  
  
  RESULTS
  The milling process made ca 1% of the lactose amorphous, however the dispersive contribution to surface energy was 31.2, 37.1, and 41.6 mJ m(-2) for crystalline, spray dried and milled lactose, respectively. A physical mixture of crystalline (99%) and amorphous (1%) material had a dispersive surface energy of 31.5 mJ m(-2).
  
  
  CONCLUSIONS
  Milling had made the surface energy similar to that of the amorphous material in a manner that was very different to a physical mixture of the same amorphous content. The milled material will have similar interfacial interactions to the 100% amorphous material.
authors.affiliation: Department of Pharmaceutics, School of Pharmacy, University of London, UK.
authors.forename: H E
authors.initials: HE
authors.lastname: Newell
authors.forename: G
authors.initials: G
authors.lastname: Buckton
authors.forename: D A
authors.initials: DA
authors.lastname: Butler
authors.forename: F
authors.initials: F
authors.lastname: Thielmann
authors.forename: D R
authors.initials: DR
authors.lastname: Williams
mesh_terms: D000465:Algorithms; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D002849:Chromatography, Gas; D003460:Crystallization; D004339:Drug Compounding; D005079:Excipients / Q000737:chemistry*; D007785:Lactose / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D005079:Excipients; D007785:Lactose