Aerosol MALDI with a Reflectron Time-of-Flight Mass Spectrometer

Abstract

Aerosol matrix-assisted laser desorption/ionization (MALDI) has been combined with a reflectron time-of-flight mass spectrometer for improved mass resolution. A methanol solution of matrix and analyte was sprayed directly into a reflectron time-of-flight mass spectrometer, and the aerosol particles were irradiated and ionized with a frequency-tripled Nd:YAG laser at 355 nm. Mass resolution of over 300 was observed for the peptides bradykinin, angiotensin II, and gramicidin D and for vitamin B(12). This represents a resolution enhancement of approximately 10-fold over that previously reported for aerosol MALDI with a linear time-of-flight instrument.

Parameters contributing to efficient ion generation in aerosol MALDI mass spectrometry

“…The high fluence required here compared with bulk was not unexpected. It has been suggested previously that residual solvent in the particles helps dissipate excess absorbed laser energy [28,33]. Other processes are likely involved as well.…”

“…It has not been as well studied as bulk MALDI, but it does provide a unique opportunity for fundamental research into the MALDI process. The analysis of aerosol particles containing analyte and matrix was first reported in 1993 by Murray and coworkers [26], who would go on to publish numerous papers on the subject [27][28][29][30][31][32][33][34]. In 1996, however, Mansoori et al were the first to analyze such particles individually in a single particle TOFMS [35].…”

337 nm Matrix-assisted laser desorption/ionization of single aerosol particles

“…The vacuum system and mass spectrometer have been described in detail previously. 10 Aerosol particles are generated at atmospheric pressure using either a piezoelectric single particle generator or a high-efficiency pneumatic nebulizer. The particles pass through a 1 mm skimmer and enter a 2 mm i.d., 25 cm long tube that directs them into a chamber maintained at 0.…”

Improved sensitivity and mass range in time-of-flight bioaerosol mass spectrometry using an electrostatic ion guide

“…Sampling standard particles composed of mixtures of matrix-assisted laser desorption ionization (MALDI) matrix and analyte provides a means to produce ions of a given m/z [3][4][5] and assess the instrument performance over a range of masses. The reflectron time-offlight (TOF) instrument was unable to detect ion signals from standard MALDI particles of angiotensin (MW ϭ 1297 Da) and ␣-cyclodextrin (MW ϭ 973 Da) but readily detected matrix ions.…”