New MALDI matrices based on lithium salts
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Systematic variation of the functional groups on the core struc-
ture can be a successful approach in the matrix engineering.[62]
Here, three new UV MALDI matrices based on the lithium salts
of aromatic acids with a better performance than the already
known LiDHB matrix were identified. Lithium vanillate, lithium
sinapate and lithium salicylate allowed for a sensitive detection
of the standards as well as analytes in the complex mixtures
of long-chain HCs and WEs. Among them, lithium vanillate
performed the best, providing the strongest signals and the most
reproducible spectra. The exceptional properties of lithium
vanillate were explained by adequate absorptions of UV radiation
and the enhanced solubility of the matrix in the organic solvents
used for the preparation of the samples of a very low polarity. In
addition, the structure of lithium vanillate may support efficient
transfer of lithium cation to the analyte in the gas phase. Lithium
vanillate tended to form homogenous deposits as evidenced
also from the SEM images of the samples. We concluded that it
might be a suitable candidate for MSI applications. We also
shortly tested lithium vanillate and LiDHB matrices with Bruker’s
UltrafleXtreme MALDI-TOF/TOF equipped with 1-kHz smartbeam
II laser at 355 nm. The matrices provided abundant signals of
[M + Li]+ both for stearyl behenate and n-triacontane indicating
that the lithium-based matrices might also be useful for MALDI
with 355-nm lasers.
Acknowledgements
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This work was supported by the Czech Science Foundation
(GACR, Project No. 203/09/0139), the Academy of Sciences of
the Czech Republic (RVO: 61388963) and Charles University in
Prague (Project SVV 260084). The authors are indebted to Kamil
Lang, Petr Rychlovský, and Stanislava Matějková for their help
with measurements and fruitful discussions.
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