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Delayed, gas‐phase ion formation in plasma desorption mass spectrometry
Author(s) -
Zubarev R. A.,
Abeywarna U.K.,
Demirev P.,
Eriksson J.,
Papaléo R.,
Håkansson P.,
Sundqvist B.U.R.
Publication year - 1997
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/(sici)1097-0231(19970615)11:9<963::aid-rcm878>3.0.co;2-#
Subject(s) - chemistry , mass spectrometry , gas phase , ion , plasma , desorption , ion mobility spectrometry–mass spectrometry , analytical chemistry (journal) , inductively coupled plasma mass spectrometry , chromatography , selected reaction monitoring , tandem mass spectrometry , adsorption , organic chemistry , physics , quantum mechanics
The formation mechanisms of secondary ions from organic targets under MeV ion bombardment were studied with a high‐resolution time‐of‐flight (TOF) mass spectrometer. Promptly formed ions H n + , C n + and C n H + were used for calibrating the TOF scale. Theoretical flight times of other ions were calculated according to the calibration curve and compared to experimentally determined values. The TOF values of non‐specific low mass fragments formed via rearrangement or breaking of several bonds and/or abstraction of several atoms, agree well with the theoretical values. On the other hand, target‐specific organic ions, including molecular ions of peptides, have longer TOF values than predicted by the calibration curve. Time delays of a few hundred picoseconds were found for low‐mass specific fragments, and a few nanoseconds for peptide molecular ions. For protonated species and non‐covalent clusters, the delays are larger than for pre‐formed and radical molecular ions. Metals contained in organic samples, as contamination, also give delayed ions. For inorganic targets of LiBF 4 , significant delays were found for the clusters (LiF) n Li + with n >3. A strong correlation was observed between the delay of an ion and the tailing of its kinetic energy distribution. The conclusion was made that the majority of target‐specific ions are formed in the gas phase, at a distance from the target surface of the order of 1 μm. © 1997 John Wiley & Sons, Ltd.