Latent Fingermarks Analysis by Imaging Mass Spectrometry

Background: Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry Imaging (MALDI-MSI) technique has been reported in the literature for fingermark analysis and forensic purposes. One of the greatest challenges in this field involves the aging of fingermarks, which has an essential role in criminal investigation. Objective: This study presents an approach to preservation fingermarks analysis through the MALDI- Fourier transform ion cyclotron resonance mass spectrometry method, comparing different matrix samples. Methods: For MALDI analysis, the efficiency of three MALDI matrices (α-cyano-4- hydroxycinnamic acid (CHCA), 2-mercaptobenzothiazole (MBT), and 2,5-dihydroxybenzoic acid (DHB)) in the ionization process of monitored analytes (m/z 368.4, m/z 522.6 and m/z 550.6) was initially evaluated, along with the spatial resolution (80 × 80 μm and 100 × 100 μm). Results: The CHCA matrix, and the resolution of 100 × 100 μm were chosen for the MALDI MSI analysis. The fingermark collections were analyzed at eight intervals from zero hours to fifty days. Additionally, photochemical aging (from zero hours to five days) of fingermarks, performed by applying constant light for five days to three different samples from the same donor, resulted in loss of chemical material and deformation of the image obtained by MALDI FT-ICR MSI analysis. On the other hand, in natural aging, the most expressive result showed that it is possible to visualize fingermark ridges of up to fifty days elapsed. Conclusion: The method proposed showed a potential for fingermark examination and application in forensic routine. Chemical imaging of fingermarks can be a useful tool in detecting and comparing evidence, even after a considerable period.