Characterization and identification of luminescent components in inks using various analytical techniques for the study of crossed-line intersections

•Temporal sequence could not be determined from the study.•Luminescent compounds were identified in formulation of inks.•Interlaboratory tests incorporated mass spectrometric and chromatographic techniques.•Crystal violet was identified in migration regions of inks in crossed-line intersections.

Several analytical instrumental techniques have been tested and utilized in an effort to determine the sequencing in crossed-line intersections (CLI) in order to gain insight into the eventual development of a standardized method to determine temporal sequence of line writing. One important facet of this study was to determine the chemical identity of the luminescent compounds present in the formulation of inks to better understand the interaction of different inks in crossed-line intersections. This study involved independent analyses of a number of inks by three laboratories. A combination of Thin Layer Chromatography (TLC), Gas Chromatography Mass Spectrometry (GC/MS), High Performance Liquid Chromatography (HPLC), Matrix-Assisted Laser Desorption Mass Spectrometry (MALDI-MS), Direct Analysis in Real Time Mass Spectrometry (DART-MS), and Liquid Chromatography Mass Spectrometry (LC-MS) were implemented by the three laboratories in order to characterize the luminescent components of inks present in crossed-line intersections. A combination of luminescent compounds including Crystal Violet and Methyl Violet were characterized and identified to be present in mixtures in the ink formulations utilizing each of the analytical techniques included in this study. However, the temporal sequence of deposition of inks present in crossed-line intersections could not be determined. The protocol described here allows for the isolation and characterization of luminescent compounds present in the formulation of inks to varying degrees, and the information presented here can be used in the future establishment of a standard protocol for the identification of luminescent compounds in inks.

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