Invited Paper AS-ThA6
Teaching Laser Desorption Mass Spectrometry Old and New Tricks in Postionization and Depth Profiling

Thursday, November 12, 2009, 3:40 pm, Room C2

Secondary ion mass spectrometry (SIMS) has seen improvements in spatial and depth resolution that now approach the tens of nanometer limit for even polymeric and biological samples. Laser desorption-based strategies such as matrix-assisted laser desorption ionization (MALDI) and laser desorption postionization mass spectrometry (LDPI-MS) [1,2] display spatial resolution that barely approaches one micron. Depth resolution in laser desorption methods is even worse at tens of microns and typically requires new sample sections to be prepared for each depth. Nevertheless, MALDI-MS and LDPI-MS remain attractive because of the more detailed chemical information they often provide, especially when applied to chemically complex samples and those with higher molecular weight species. Ultrashort pulse laser irradiation is known to cause minimal laser induced damage when interacting with soft biological materials. Data will be presented evaluating the prospects for employing ultrashort laser pulses for depth profiling in mass spectrometric imaging. Ongoing experiments utilizing single photon ionization of laser desorbed neutrals via vacuum ultraviolet radiation will also be presented for detection and selectivity that are complementary to MALDI-MS. These strategies will be applied to the analysis of molecular analytes within intact bacterial biofilms grown on biomaterials surfaces.

[1] L. Hanley and R. Zimmermann, Anal. Chem., to be published June 2009.

[2] G.L. Gasper, R. Carlson, A. Akhmetov, J.F. Moore, and L. Hanley, Proteom. 8 (2008) 3816.