Ink identification by time-of-flight secondary ion mass spectroscopy

This work is devoted to the secondary ion mass spectroscopic application in the studies of ink layering on paper. Optical methods are often unreliable in the identification of ink layering on substrates. We demonstrated the power of time-of-flight secondary ion mass spectroscopy (ToF-SIMS) by measuring the secondary ion mass spectra of handwriting on paper and assessing the characteristic ions for each colored ink. These ions were then used to collect images from overlapping handwritings. It was shown that the method could reliably determine which color was applied to the paper first. This work has potential applications in forensic studies.