|AVS 57th International Symposium & Exhibition|
|Applied Surface Science||Wednesday Sessions|
|Session:||Surface Mass Spectrometry: SIMS and Beyond|
|Presenter:||J. Matsuo, Kyoto University, CREST, Japan|
|Authors:||J. Matsuo, Kyoto University, CREST, Japan
H. Yamada, Kyoto University, Japan
Y. Wakamatsu, Kyoto University, Japan
T. Aoki, Kyoto University, CREST, Japan
T. Seki, Kyoto University, CREST, Japan
|Correspondent:||Click to Email|
Because of the complexity of the structure and chemical composition in living organisms, much progress has been made in realizing mass imaging for biological samples. Secondary ion mass spectrometry (SIMS) imaging technique has the significant advantage of high spatial resolution, free of matrix deposition and with good reproducibility. In conventional SIMS the primary probes are keV-energy ion beams, which deposit their energy to atomic nuclei. As a result, primary ions break molecular bonding, and molecular information is lost. On the other hand, MeV-energy ions enhance ionization of high mass molecules, because of their dense electronic excitation. Molecular images with lateral resolution of around 5 mm have been demonstrated for peptides or lipids using MeV-energy ion beams .
In addition, MeV-energy ions, which have a long projection range in matter, can be utilized for material analysis under low vacuum. The low-vacuum condition prevents evaporation of water from the biological sample and helps maintain the shape of the sample. A new instrument has been developed to realize SIMS measurements under low vacuum. Biological samples were analyzed with swift heavy ions, and secondary molecular ions were introduced into a quadrupole ion guide combined with a differential pumping system. An orthogonal time-of-flight (o-ToF) retaining high vacuum was employed to measure secondary ion mass spectra. This system allows the use of continuous beam, because of collisional cooling and orthogonal extraction. The mass resolution of this system is better than 6000, and is independent on the primary beam. Molecular imaging of cells and tissues was observed with a sample-scanning system. Secondary emitted biomolecular ions, such as lipids or cholesterols, were clearly observed with sufficiently high intensity. This new technique opens new possibilities for SIMS analysis, and we called it “wet SIMS”.
Recent progress in this novel technique will be presented and discussed in view of its possible application in the analysis of biological matter.
 Y. Nakata, et al. J. Mass Spectrom. (2009) 44, 128–136