Depth-Dependent Chemical Analysis of Handwriting by Nanospray Desorption Electrospray Ionization Mass Spectrometry

Gwangbin Lee, Sangwon Cha

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

Abstract

Nanospray desorption electrospray ionization (nano-DESI) has been utilized in direct sampling mass spectrometry (MS) that requires highly spatially resolved sampling with minimal sample destruction. In this study, we explored the applicability of nano-DESI MS for the forensic chemical analysis of ink directly from handwriting on paper. Nano-DESI readily ionizes dyes, including the polyanionic ones, with minimal fragmentation and produces chemical fingerprints of ballpoint pens directly from a paper surface. Further, we specifically focused on how the potential of nano-DESI that changes the mass spectral profiles over time could reflect the differential distribution of analytes in a vertical direction because mildly extracted analytes are immediately transferred and analyzed in real time. To test this, we wrote the character "X"with various combinations of two different pens and analyzed the crosspoints by nano-DESI MS. As a result, the time-course changes in the chemical fingerprints of the ink, which were consistent with the order of the pen strokes, were successfully obtained by nano-DESI MS in most cases. After confirming the capability of the depth-dependent analysis of nano-DESI MS, we analyzed a simulated forgery in which the original and forged writings were made before and after affixing a seal and clearly distinguished the two portions based on the time-dependent changes in the profile of the ink compound.

Original languageEnglish
Pages (from-to)315-321
Number of pages7
JournalJournal of the American Society for Mass Spectrometry
Volume32
Issue number1
DOIs
StatePublished - 6 Jan 2021

Keywords

  • ambient desorption ionization
  • direct sampling mass spectrometry
  • forensic analysis
  • handwriting
  • ink
  • nanospray desorption electrospray ionization

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