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 obtai ned from single biological aerosol particles using an aerosol time-of-fligh t mass spectrometer (ATOFMS). The inlet to the ATOFMS was coupled with an e vaporation/condensation how cell that allowed the aerosol to be coated with matrix material as the sampled stream entered the spectrometer, Mass spect ra were generated from aerosol composed either of gramicidin-S or erythromy cin, two small biological molecules, or from aerosolised spores of Bacillus subtilis var niger. Three different matrices were used: 3-nitrobenzyl alco hol, picolinic acid and sinapinic acid. A spectrum of gramicidin-S was gene rated from approximately 250 attomoles of material using a molar ratio of 3 -nitrobenzyl alcohol to analyte of approximately 20:1, A single peak, locat ed at 1224 Da, was obtained from the bacterial spores, The washing liquid a nd extract solution from the spores were analyzed using electrospray mass s pectrometry and subsequent MS/MS product ion experiments. This independent analysis suggests that the measured species represents part of the B, subti lis peptidoglycan. The on-line addition of matrix allows quasi-real-time ch emical analysis of individual, aerodynamically sized particles, with an ove rall system residence time of less than 5 seconds. These results suggest th at a MALDIATOFMS can provide nearly real-time identification of biological aerosols, Copyright (C) 2000 John Wiley & Sons, Ltd.