Remote Deep-Ultraviolet Laser Ablation in Connection with Electrospray Ionization–Atmospheric Pressure Chemical Ionization (rDUVLAESCI): A Novel Dual Ionization Source for Molecular Mass Spectrometry

Abstract

A novel remote deep ultraviolet laser ablation inlet connected to a dual electrospray ionization–atmospheric pressure chemical ionization (rDUVLAESCI) source is presented. This system allows for the simultaneous and spatial acquisition of mass spectrometry (MS) data for organic molecules with diverse polarities and molecular weights. Deep 193 nm UV laser ablation was used to sample analytes from dried spots for molecular MS analysis precisely. Furthermore, molecular MS imaging (MSI) with a variable laser spot size down to 3 μm was demonstrated. The complementary ionization modes generated mass spectra with sufficient analyte signals, detecting a broad range of molecules from polar compounds like caffeine and PEG 600, to nonpolar analytes, such as anthracene and wax esters, all within a single analytical run. Detection limits were found in the tens of attomoles per ablated/desorbed pixel. The powerful capabilities of the fully automated rDUVLAESCI dual source were demonstrated by visualizing the spatial distribution of new psychoactive substances on latent fingerprints. MSI for both sebum components and psychoactive substances revealed a connection between the chemical evidence and biometrical information. The rDUVLAESCI–MSI enabled the unambiguous identification of individuals, even using partially overlapped latent fingerprints. This unique rDUVLAESCI approach, with its remote laser ablation unit, improved spatial resolution and analyte coverage, particularly for nonpolar compounds.