Laser Pulse Width Dependence and Ionization Mechanism of Matrix-Assisted Laser Desorption/Ionization

• Published in: Journal of the American Society for Mass Spectrometry Vol. 28; no. 10; pp. 2235 - 2245
• Main Authors: Liang, Sheng-Ping, Lu, I-Chung, Tsai, Shang-Ting, Chen, Jien-Lian, Lee, Yuan Tseh, Ni, Chi-Kung
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.10.2017; Springer Nature B.V
• Subjects: Analytical Chemistry; Bioinformatics; Biotechnology; Chemistry; Chemistry and Materials Science; COMPARATIVE EVALUATIONS; Computer simulation; COMPUTERIZED SIMULATION; DESORPTION; Dihydroxybenzoic acid; Extreme values; FORECASTING; Hydroxycinnamic acid; INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; IONIZATION; Ions; LASERS; MASS SPECTRA; Mass spectrometry; Mass spectroscopy; Mathematical models; MULTI-PHOTON PROCESSES; Organic Chemistry; Proteomics; PROTONS; Pulse duration; Research Article; ULTRAVIOLET RADIATION; Velocity distribution; Ion-to-neutral ratio; Ionization mechanism; MALDI; CPCD model; Thermal model; Multiphoton ionization; Laser pulse width
• ISSN: 1044-0305; 1879-1123
• DOI: 10.1007/s13361-017-1734-8

Ultraviolet laser pulses at 355 nm with variable pulse widths in the region from 170 ps to 1.5 ns were used to investigate the ionization mechanism of matrix-assisted laser desorption/ionization (MALDI) for matrices 2,5-dihydroxybenzoic acid (DHB), α-cyano-4-hydroxycinnamic acid (CHCA), and sinapinic acid (SA). The mass spectra of desorbed ions and the intensity and velocity distribution of desorbed neutrals were measured simultaneously for each laser shot. These quantities were found to be independent of the laser pulse width. A comparison of the experimental measurements and numerical simulations according to the multiphoton ionization, coupled photophysical and chemical dynamics (CPCD), and thermally induced proton transfer models showed that the predictions of thermally induced proton transfer model were in agreement with the experimental data, but those of the multiphoton ionization model were not. Moreover, the predictions of the CPCD model based on singlet–singlet energy pooling were inconsistent with the experimental data of CHCA and SA, but were consistent with the experimental data of DHB only when some parameters used in the model were adjusted to extreme values. Graphical Abstract ᅟ