Identification of Dyes in Pen Ink by High Resolution Mass Spectrometry: A Laboratory Experiment

摘要

In this experiment, students develop their knowledge of mass spectrometry to identify dyes in different commercial pen ink entries on paper using a simple method based on liquid-solid extraction and high-resolution mass spectrometry. In short, students will first extract the dyes in the ink from the paper with a 1:1 solution of water and methanol. The sample is then analyzed by matrix assisted laser desorption/ionization quadrupole time-of-flight mass spectrometer (MALDI-QTOFMS). Inks from three commercial inks were analyzed and they could be differentiated according to the presence of peaks in the mass spectrum corresponding to specific dyes. Key concepts in mass spectrometry such as resolution, mass accuracy and formula determination can be taught with the acquired data. A forensic activity could also be added to enhance the interest of students for mass spectrometry and its applications. This laboratory experiment is expected to be performed in a four-hour laboratory period by sophomore or junior students. To summarize, this experiment provides an interesting introduction to fundamental concepts of mass spectrometry.