Solvent-free silver-nanoparticle surface-assisted laser desorption/ionization imaging mass spectrometry of the Irganox 1010 coated on polystyrene

•SALDI-IMS is performed using silver nanoparticles.•Silver nanoparticles are deposited on the sample surface for SALDI-IMS.•The lateral resolution is 20 μm.•The probing depth is 50–100 nm.

Imaging mass spectrometry (IMS) of the antioxidant Irganox 1010 coated on a polystyrene (PS) was conducted using solvent-free silver-nanoparticle surface-assisted laser desorption/ionization (Ag-NP SALDI). The lateral resolution and probing depth of Ag-NP SALDI-IMS, which are important factors in determining the surface sensitivity, were investigated. Direct Ag vapor deposition produced a 10-nm-thick homogenous layer of Ag-NPs on the Irganox 1010/PS thin film. Ag adduct ions of Irganox 1010 and PS repeating structures, and Ag cluster ions appeared in the mass spectrum, which showed that Ag-NPs on the sample surface enhanced the ionization efficiency by functioning as cationization agents. At the lateral resolution of this method (20 μm), complementary grid patterns (55 lines per inch) of Irganox 1010 on the PS were observed. The probing depth was investigated with Irganox 1010 layers of different thicknesses, the detection of silver adduct ions of PS indicated Ag-NP SALDI could ionize the PS layer beyond the Irganox 1010 layer. The probing depth was 50–100 nm for 10-nm-thick Ag-NP SALDI.

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