LASER-ABLATION OF ORGANIC-MOLECULES FROM FROZEN MATRICES

被引:20
作者
BELOV, ME
ALIMPIEV, SS
MLYNSKY, VV
NIKIFOROV, SM
DERRICK, PJ
机构
[1] RUSSIAN ACAD SCI, INST GEN PHYS, MOSCOW 117942, RUSSIA
[2] UNIV WARWICK, DEPT CHEM, INST MASS SPECTROMETRY, COVENTRY CV4 7AL, W MIDLANDS, ENGLAND
关键词
D O I
10.1002/rcm.1290091420
中图分类号
Q5 [生物化学];
学科分类号
071010 ; 081704 ;
摘要
The technique of frozen matrix-assisted laser ablation coupled with resonance-enhanced multiphoton ionization and reflectron time-of-flight mass spectrometry was used to detect intact organic molecules directly from solutions. When frozen at the temperature of liquid nitrogen, the matrices of interest were ablated by a pulsed CO2 single-mode laser. The analyte molecules emerging from the ablated plume were then ionized by a tunable XeCl excimer laser-pumped dye laser and analysed with a gridless reflectron time-of-flight mass spectrometer. The ablation process from an ice matrix was studied with the amino acids tryptophan and tyrosine dissolved in an aqueous ethanol solution to a concentration level of 5 x 10(-4) M. It was found that fragmentation of the analyte molecules is strongly dependent on the ablating laser fluence and that there is a laser fluence range just above the ablation threshold where the decomposition is negligible. The different fragmentation mechanisms are discussed and a cavitation under the liquid surface, causing the sonoluminescence signal from an ice matrix, was shown to be responsible for the decomposition of the analyte molecules ablated by a low photon energy IR laser. Under the appropriate conditions, the analyte molecules were found to have a low rotational temperature of about 150 K resulting from the jet-like cooling in multiple collisions with matrix molecules.
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页码:1431 / 1436
页数:6
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