Laser power dependence of mass spectral signatures from individual bacterial spores in bioaerosol mass spectrometry |
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Authors: | Steele Paul T Tobias Herbert J Fergenson David P Pitesky Maurice E Horn Joanne M Czerwieniec Gregg A Russell Scott C Lebrilla Carlito B Gard Eric E Frank Matthias |
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Affiliation: | Lawrence Livermore National Laboratory, 7000 East Avenue, L-174, Livermore, California 94550, USA. |
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Abstract: | Bioaerosol mass spectrometry is being developed to analyze and identify biological aerosols in real time. Characteristic mass spectra from individual bacterial endospores of Bacillus subtilis var. niger were obtained in a bipolar aerosol time-of-flight mass spectrometer using a pulsed 266-nm laser for molecular desorption and ionization. Spectra from single spores collected at an average fluence of approximately 0.1 J/cm2 frequently contain prominent peaks attributed to arginine, dipicolinic acid, and glutamic acid, but the shot-to-shot (spore-to-spore) variability in the data may make it difficult to consistently distinguish closely related Bacillus species with an automated routine. Fortunately, a study of the laser power dependence of the mass spectra reveals clear trends and a finite number of "spectral types" that span most of the variability. This, we will show, indicates that a significant fraction of the variability must be attributed to fluence variations in the profile of the laser beam. |
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