Anal. Chem. 2003, 75, 4373-4381
Using Matrix Peaks To Map Topography: Increased Mass Resolution and Enhanced Sensitivity in Chemical Imaging Liam A. McDonnell,† Todd H. Mize,† Stefan L. Luxembourg,† Sander Koster,‡ Gert B. Eijkel,† Elisabeth Verpoorte,‡ Nico F. de Rooij,‡ and Ron M. A. Heeren*,†
FOM Institute for Atomic and Molecular Physics, Kruislaan 407, 1098 SJ, Amsterdam, The Netherlands, and Institute of Microtechnology, University of Neuchaˆ tel, Rue Jaquet-Droz 1, 2007 Neuchaˆ tel, Switzerland
Chemical imaging mass spectrometry1,2 is a powerful technique that combines the chemical information of mass spectrometry3 with the spatial distribution information of a microscope. In principle, this multidimensional technique can be applied to any system to help identify the components present in a sample as well as locate the positions where the components are present. In practice, chemical imaging can be separated into two regimes, low mass + high spatial resolution and high mass + low spatial resolution. This distinction reflects the different ionization techniques used. Matrix-assisted laser desorption/ionization (MALDI)4,5 chemical imaging6-8 is currently performed by rastering the sample through the laser probe. For each position, a mass spectrum is
recorded. Once the experiment is complete the chemical images of each mass can be calculated. MALDI imaging has mostly been used to map the distribution of proteins in biological tissue. However, the spatial resolution typically obtained, g25 µm,8 permits only variations on a larger scale to be identified. Although a MALDI chemical imaging mass spectrometer was recently developed that permits much higher spatial resolutions to be obtained,9 it is noteworthy that high-mass high spatial resolution images are still to be published. Using secondary ion mass spectrometry (SIMS)10,11 it has proven possible to resolve features that have dimensions of
