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Platinum vapor deposition surface-assisted laser desorption/ionization for imaging mass spectrometry of small molecules


H. Kawasaki, Department of Chemistry and Materials Engineering, Faculty of Chemistry, Materials, and Bioengineering, Kansai University, 3-3-35 Yamate-cho, Suita-shi, Osaka 564-8680, Japan.




Matrix-assisted laser desorption/ionization (MALDI) imaging mass spectrometry (IMS) allows for the simultaneous detection and imaging of several molecules in a sample. However, when using an organic matrix in the MALDI-IMS of small molecules, inhomogeneous matrix crystallization may yield poorly reproducible peaks in the mass spectra. We describe a solvent-free approach that employs a homogeneously deposited metal nanoparticle layer (or film) for small-molecule detection.


Platinum vapor deposition surface-assisted laser desorption/ionization imaging mass spectrometry (Pt vapor deposition SALDI-IMS) of small molecules was performed as a solvent-free and organic-matrix-free method. A commercially available magnetron sputtering device was used for Pt deposition. Vapor deposition of Pt produced a homogenous layer of nanoparticles over the surface of the target imaging sample.


The effectiveness of Pt vapor deposition SALDI-IMS was demonstrated for the direct detection of small analytes of inkjet ink on printed paper as well as for various other analytes (saccharides, pigments, and drugs) separated by thin-layer chromatography (TLC), without the need for extraction or concentration processes. The advantage of choosing Pt instead of Au in SALDI-IMS was also shown.


A solvent-free approach involving the direct deposition of Pt on samples (SALDI-IMS) is effective for the analysis of inkjet-printed papers and various analytes separated by TLC. This method would be useful in imaging analyses of various insulating materials such as polymers and biological materials. Copyright © 2012 John Wiley & Sons, Ltd.