Fluorinated surfaces: smart substrates for matrix‐free laser desorption ionization

Abstract

Matrix Assisted Laser Desorption Ionization (MALDI) is a soft ionization method that finds widespread applications in high-throughput mass spectrometric analysis. One of the main limit of this technique is that it requires the use of matrices: these molecules enable the analytes desorption and ionization (D/I) processes but also generate strong interfering signals in the low mass spectral region, preventing a suitable detection of low molecular weight compounds. The possibility to avoid their use will ease both sample preparation and mass spectrum (MS) interpretation. In recent years nanostructured surfaces have been proposed as a viable method to achieve such goal but the results are limited to specific classes of chemical compounds and the approach lacks in generality. Here we demonstrate that the fluorination of surfaces is the only step needed to activate the target and to achieve matrix-free operation with the same detection limit obtained using nanostructured chips. The results of this work suggest that D/I is a purely interfacial effect, with negligible contribution from chemical nature of the underlying substrate, provided that the substrate is conductive and able to efficiently absorb the UV laser beam.

Mass Spectrometry for Single-Cell Analysis

“…LDI technique can be matrix-free or matrix-assisted laser desorption/ionization in nature. Matrix-free LDI spectrometry is well suitable for plant and algae cells due to their greater number and present of pigmented molecules that can easily absorb laser light (Piotto et al 2017;Le Pogam et al 2015;Qureshi et al 2013). Whereas animal cells are comparatively small in number and lack the pigmented molecules.…”