title: Detection and imaging of thermochromic ink compounds in erasable pens using desorption electrospray ionization mass spectrometry.
abstract: BACKGROUND
  Thermochromic ink pens are widely accessible worldwide and have gained popularity among the general public. These pens are very useful to undo mistakes while writing important documents or exams. They are also, however, misused in committing crimes such as counterfeiting checks or wills. Thus, the forensics community is in need of techniques that will allow these forgeries to be detected rapidly, reliably and conveniently.
  
  
  METHODS
  Thermochromic ink compounds were investigated using Desorption Electrospray Ionization (DESI) coupled with an LTQ mass spectrometer and Thin-Layer Chromatography (TLC). Tandem mass spectrometric analysis was conducted using Electrospray Ionization (ESI) coupled with an Orbitrap LTQ mass spectrometer performing Collision-Induced Dissociation (CID) for identification of ink traces.
  
  
  RESULTS
  Chemical marker ions characteristic of the state of ink (visible or invisible) were identified and mapped in ink traces by the use of DESI-MS imaging. These ions can be employed by forensic experts as fingerprint markers in forged documents. The marker ions were also characterised by conducting tandem mass spectrometry using paper spray in an Orbitrap LTQ mass spectrometer.
  
  
  CONCLUSIONS
  Specific chemical components yielding ions of m/z 400, 405, 615 and 786 were distinguished as only being apparent in the invisible and reappeared state of the ink. The absence of these compounds in the original state of the ink enabled their recognition as useful chemical determinants in detecting forgery. DESI-MSI was thus shown to be a very useful, convenient and reliable technique for detecting forgery in paper documents due to its fast and reproducible mode of analysis, with no sample preparation and minimal damage to the document under investigation. Copyright © 2017 John Wiley & Sons, Ltd.
authors.affiliation: Centre for Research in Mass Spectrometry (CRMS), Department of Chemistry, York University, Toronto, Canada.
authors.forename: Amin
authors.initials: A
authors.lastname: Khatami
authors.affiliation: Centre for Research in Mass Spectrometry (CRMS), Department of Chemistry, York University, Toronto, Canada.
authors.forename: Shamina S
authors.initials: SS
authors.lastname: Prova
authors.affiliation: Centre for Research in Mass Spectrometry (CRMS), Department of Chemistry, York University, Toronto, Canada.
authors.forename: Aafreen K
authors.initials: AK
authors.lastname: Bagga
authors.affiliation: Centre for Research in Mass Spectrometry (CRMS), Department of Chemistry, York University, Toronto, Canada.
authors.forename: Michelle
authors.initials: M
authors.lastname: Yan Chi Ting
authors.affiliation: Centre for Research in Mass Spectrometry (CRMS), Department of Chemistry, York University, Toronto, Canada.
authors.forename: Gurnoor
authors.initials: G
authors.lastname: Brar
authors.affiliation: Centre for Research in Mass Spectrometry (CRMS), Department of Chemistry, York University, Toronto, Canada.
authors.forename: Demian R
authors.identifier: http://orcid.org/0000-0002-5804-1302
authors.initials: DR
authors.lastname: Ifa