Systematic method optimisation approach for small molecule imaging on the SELECT SERIES MALDI MRT - Drug mapping in fingerprints, a case study.

Molecular fingerprinting via Matrix Assisted Laser Desorption Ionisation time-of-flight Mass Spectrometry profiling (MALDI MSP) and Imaging (MALDI-MSI) has been proven to provide biometric and lifestyle information from a fingermark. As such, it can be an effective tool to assist police investigations, thus justifying continued effort to improve the quality and range of the forensic intelligence that it is possible to provide. We are currently exploring the advancements in molecular fingerprinting capabilities on the state-of-the -art SELECT SERIES MALDI-MRT mass spectrometer based on its high mass measurement accuracy (sub-ppm) and spatial resolution (15 μm). The unique nature of this instrument requires careful optimisation to maximise the system's performance for the imaging of small molecules in fingerprints. In this study, a systematic approach to setting optimisation including optimisation of laser parameters, source voltage, quadrupole MS profile, and Transfer gas as well as RF voltage settings were determined for the analysis of latent fingerprint imaging and antipsychotics-contaminated fingerprint imaging. The developed method eventually yields significant improvement in image resolution over the default parameters.