Novel strategies for desorption mass spectrometry

                                       Mgr. Antonín Bednařík

Supervisor:                                                doc. Mgr. Jan Preisler, Ph.D.

Development of new analytical instrumentation, sample preparation, sampling modes and sample
introduction techniques related to matrix-assisted laser desorption/ionization time-of-flight mass
spectrometry (MALDI TOF MS) imaging and inductively-coupled plasma mass spectrometry (ICP MS) are
presented.

MALDI TOF MS imaging is a rapidly evolving technique enabling the mapping of compounds present in
biological tissue sections. Despite the recent introduction of high-repetition rate lasers to TOF
MS instruments, obtaining a single high-resolution image requires a few hours. A substantial
increase in the throughput of the TOF MS-based tissue imaging can be achieved by introducing of the
new laser beam scanning sampling mode. In this mode, high-speed precision scanning of the laser
beam along the imaged sample surface is used to overcome a slower sample target translation
realized by motorized stages in MALDI TOF MS imaging. An axial MALDI TOF MS instrument utilizing a
4-kHz UV laser and high-speed optical scanning system was constructed in our laboratory. The
instrument recorded a 100 × 100 pixel MS image in ∼11 min using 100 laser shots per pixel. This is
almost an order of magnitude faster when compared to a modern commercial instrument equipped with
1-kHz laser.

Matrix application to a surface of the biological tissues is a crucial step in successful MALDI
imaging experiment. Several techniques of matrix deposition, namely airbrush deposition,
electrospray deposition, nano-spotting and sublimation were developed. The most promising
techniques were used for MALDI MS imaging of lipids in mouse brain tissue.

A diode laser thermal vaporization (DLTV) is a sample introduction technique to ICP, which presents
a low-cost alternative to the commercial laser-ablation systems and nebulizers. DLTV employs a
diode laser with power sufficient to induce ablation/pyrolysis of the substrate, typically a common
filter paper overprinted with a black ink. Submicroliter liquid sample volumes are deposited
without any treatment on the substrate, dried, vaporized in the laser ablation chamber and the
generated aerosol is then carried into the ICP mass spectrometer. New substrate for DLTV, cellulose
thin-layer chromatography (TLC) sheets was introduced and the coupling of ICP MS with the TLC
separation will be discussed.


We gratefully acknowledge the financial support of the Czech Science Foundation (Grants
GAP206/10/J012 and GAP206/12/0538), the project “CEITEC - Central European Institute of Technology”
(Grant CZ.1.05/1.1.00/02.0068) from European Regional Development Fund and the program of
“Employment of Newly Graduated Doctors of Science for Scientific Excellence” (Grant
CZ.1.07/2.3.00/30.009) co-financed from the European Social Fund and the state budget of the Czech
Republic.