Development of Laser Desorption Imaging Mass Spectrometry Methods to Investigate the Molecular Composition of Latent Fingermarks

Abstract

Abstract. For a century, fingermark analysis has been one of the most important and common methods in forensic investigations. Modern chemical analysis technologies have added the potential to determine the molecular composition of fingermarks and possibly identify chemicals a suspect may have come into contact with. Improvements in analytical detection of the molecular composition of fingermarks is therefore of great importance. In this regard, matrix-assisted laser desorption ionization (MALDI) and laser desorption ionization (LDI) imaging mass spectrometry (IMS) have proven to be useful technologies for fingermark analysis. In these analyses, the choice of ionizing agent and its mode of deposition are critical steps for the identification of molecular markers. Here we propose two novel and complementary IMS approaches for endogenous and exogenous substance detection in fingermarks: sublimation of 2-mercaptobenzothiazol (2-MBT) matrix and silver sputtering.

Development of operational protocols for the analysis of primary and secondary fingermark lifts by MALDI-MS imaging

“…Given the huge potential in informing both investigations and judicial debates, as well as the opportunity offered at the time to only work with secondary lifts, there were grounds justifying the undertaking of further developmental work to devise optimal methods for sample treatment of secondary lifts; additionally, while a few other groups have now published reports on the use of MALDI-MS based methods for the chemical mapping of fingermarks [7][8][9][10][11] , none of these studies has dealt with secondary lifts. There are indeed different ways to treat such samples: (a) recovering the fingermark residue remaining after the primary lift with no prior attempt to re-enhance the residue, followed by matrix spray-coating for direct MALDI MS-Imaging/Profiling analysis; (b) subjecting the fingermark residue remaining after the primary lift to a secondary lift following reenhancement using the same FET initially employed, with this lift being subsequently subjected to matrix spray-coating for direct MALDI-MS Imaging/Profiling analysis; (c) prior to MALDI-MS Imaging/Profiling analysis, subjecting the fingermark residue remaining after the primary lift to a secondary lift following re-enhancement by the Dry-Wet method 12,13 with the sample being subsequently either (c-1) spray-coated using a suitable solvent in which both the matrix and analytes can dissolve 12 or (c-2) matrix spray-coated with the matrix re-enhancement using the dry powder as a seeding layer for the co-crystallisation formation 14 .…”

Lifestyle chemistries from phones for individual profiling

“…Although no approach has been developed yet to capture such lifestyle-derived skin-associated chemicals from objects, the detection of molecular traces from the skin has been used in the past and involves very sensitive techniques. Due to its superb sensitivity (14), mass spectrometry (MS) is a powerful tool widely used for forensic applications (15) by providing either molecular (16)(17)(18)(19) or elemental analysis (20)(21)(22). Specific sets of known molecules are usually targeted in forensics applications, for example, to identify traces of illicit drugs or explosives (23)(24)(25)(26).…”

An update on MALDI mass spectrometry based technology for the analysis of fingermarks – stepping into operational deployment

“…Ag sputtering has shown to generate very neat and high resolution images of latent fingermarks 15 . However, detection and imaging capabilities were only, so far, shown for lipids and ditallowdimethylammonium ions.…”

“…In their report, Lauzon et al 15 , subjected a range of known MALDI matrices to sublimation in order to visualise and analyse fingermarks, showing the ability to map diacyl and triacylglycerols (DAGs and TAGs) onto the fingermark's ridges. However, this method may potentially bear a limitation to operational deployment.…”