Michael Anthony Stowers

Application of matrix‐assisted laser desorption/ionization to on‐line aerosol time‐of‐flight mass spectrometry

Matrix-assisted laser desorption/ionization (MALDI) mass spectra were obtained from single biological aerosol particles using an aerosol time-of-flight mass spectrometer (ATOFMS). The inlet to the ATOFMS was coupled with an evaporation/condensation flow cell that allowed the aerosol to be coated with matrix material as the sampled stream entered the spectrometer. Mass spectra were generated from aerosol composed either of gramicidin-S or erythromycin, two small biological molecules, or from aerosolised spores of Bacillus subtilis var niger. Three different matrices were used: 3-nitrobenzyl alcohol, picolinic acid and sinapinic acid. A spectrum of gramicidin-S was generated from approximately 250 attomoles of material using a molar ratio of 3-nitrobenzyl alcohol to analyte of approximately 20:1. A single peak, located at 1224 Da, was obtained from the bacterial spores. The washing liquid and extract solution from the spores were analyzed using electrospray mass spectrometry and subsequent MS/MS product ion experiments. This independent analysis suggests that the measured species represents part of the B. subtilis peptidoglycan. The on-line addition of matrix allows quasi-real-time chemical analysis of individual, aerodynamically sized particles, with an overall system residence time of less than 5 seconds. These results suggest that a MALDI-ATOFMS can provide nearly real-time identification of biological aerosols. Copyright 2000 John Wiley & Sons, Ltd.

Fluorescence preselection of bioaerosol for single-particle mass spectrometry.

We have designed, constructed, and tested a system that pre-selects the biological fraction of airborne particles from the overall aerosol. The preselection is based on fluorescence emission excited by a continuous 266 nm laser beam. This beam is one of two cw beams used to measure the aerodynamic particle size of sampled particles. The intention in our system is that single particles, based on size and fluorescence emission, can be selected and further examined for chemical composition by mass spectrometry.

Development of Bioaerosol Alarming Detector

Although banned by the BTWC in 1972, biological warfare agents continue to be a threat to military and public health. Countermeasures can only be effective if rapid detection and reliable identification techniques are in place. TNO Prins Maurits Laboratory, and Delft University of Technology and Bruker-Daltonik (Germany) are developing an bioaerosol alarm detector, based on fluorescence pre-selection, Aerosol Time-of-Flight Mass Spectrometry (ATOFMS) and Matrix-Assisted Laser Desorption/Ionization (MALDI). Using this combination, mass spectra were obtained from single biological aerosol particles.