Professor – Analytical Chemistry, Aerosols Analysis, Mass Spectrometry

Research and/or Creative Works

The research interests of our group lie in the general field of aerosol analysis. Present investigations involve the simultaneous physical and chemical characterization of individual particles, leading to the rapid, on-line physico-chemical characterization of the aerosol.

The importance of aerosol science has increased dramatically in recent years. Aerosols contribute to a variety of environmental, biological, and industrial processes including air pollution (acid deposition, global warming), human health (morbidity, mortality, medicine delivery), combustion (soot and soot precursors), materials synthesis (nanoparticles, coatings) and clean room technology (quality control). Of particular interest is the adoption of the National Ambient Air Quality Standard (PM2.5) that discriminates aerosol toxicity on the basis of aerodynamic particle diameters. In addition, particle-bound toxins, such as polyaromatic hydrocarbons (PAHs) or dioxins, may exhibit enhanced toxicological behavior in the particle phase as opposed to the gas phase.

Our group is developing an instrument for the real-time physical and chemical characterization of aerosols on a single particle basis. This technique involves laser desorption/ionization of particles followed by time-of-flight mass spectrome-try. The aerosol mass spectrometer (AMS) shown below consists of 3 components: 1) particle inlet; 2) laser ionization laser; 3) mass spectrometer. The particle inlet can simultaneously collimate an aerosol into a compact beam and selectively sample particles of a pre-determined diameter. This selectivity provides an inherent means of particle size determi-nation. Once the particles have been sized, individual particles are vaporized into ionic components with a pulsed, high-power laser. The representative positive and negative ion bursts are then identified by bipolar time-of-flight mass spectrometry. In this manner, we obtain a correlated description of the aerodynamic size and chemical composition of single particles. With rapid, replicate measurements, these single particle analyses provide a detailed description of the entire aerosol sample.

Presently our research follows two general directions: ultrafine (sub-200 nm diameter) particle detection and the chemical analysis of particle-bound organic molecules. Both types of particles exhibit a high potential for human toxicity. The detection of ultrafine particles is a challenge that tests the pressure-dependent selectivity of the inlet. An extensive characterization of the inlet is necessary for the preferential, efficient, and reproducible sampling of ultrafine particles. The qualitative analysis of particle-bound organics is complicated by spontaneous molecular fragmentation that occurs during ionization. Research in our group is underway to devise softer, resonant ionization schemes that minimize undesired fragmentation. A long-term goal of this research is the development of aerosol mass spectrometry as a real-time, field-ready, qualitative and quantitative monitor for common organic pollutants like PAHs.


J. Zahardis, S. Geddes and G.A. Petrucci, "Improved Understanding of Atmospheric Organic Aerosols via Innovations in Soft Ionization Aerosol Mass Spectrometry", Anal. Chem., 83 (7), 2409-2415 (2011) [Cover Feature Article]

S. Geddes, B. Nichols, S. Flemer Jr., J. Eisenhauer, J. Zahardis and G.A. Petrucci, "Near-Infrared Laser Desorption/Ionization Aerosol Mass Spectrometry for Investigating Primary and Secondary Organic Aerosols under Low Loading Conditions," Anal. Chem., 82(19) 7915-7923 (2010).

S. Geddes, B. Nichols, K. Todd, J. Zahardis and G.A. Petrucci, "Near-infrared laser desorption/ionization aerosol mass spectrometry for measuring organic aerosol at atmospherically relevant aerosol mass loadings", Atmos. Measu. Tech., 3, 1175-1183 (2010).

S. Geddes, J. Zahardis and G.A. Petrucci, "Chemical transformations of peptide containing fine particles: oxidative processing, accretion reactions and implications to the atmospheric fate of cell-derived materials in organic aerosol", J. Atmos. Chem., 63(3), 187-202 (2009).

S. Geddes, J. Zahardis, J. Eisenhauer, and G.A. Petrucci, "Low energy photoelectron capture resonance ionization aerosol mass spectrometry of small peptides with Cysteine residues: Cys-Gly, -Glu-Cys and glutathione" Int. J. Mass Spectrom, 282(1-2), 13-20 (2009).

J.P. Stevens, J. Zahardis, M. MacPherson, B.T. Mossman and G.A. Petrucci, "A new method for quantifiable and controlled dosage of particulate matter for in vitro studies: the electrostatic particulate dosage and exposure system (EPDExS)",Toxicol. In Vitro, 22, 1768-1774 (2008).

K.A. Puzey, P.J. Gardner, V.K. Petrova, C.W. Donnelly and G.A. Petrucci, "Automated species and strain identification of bacteria in complex matrices using FTIR spectroscopy", Proceedings of the SPIE (International Society for Optical Engineering), Chemical, Biological, Radiological, Nuclear, Explosive Sensors IX, 2008

J. Zahardis, S. Geddes and G.A. Petrucci, "The ozonolysis of primary aliphatic amines in single and multicomponent fine particles," Atmos. Chem. Phys., 8, 1181-1194 (2008).

J. Zahardis, S. Geddes and G.A. Petrucci, "Detection of free amino acids in proxies of marine aerosol by photoelectron resonance capture ionization aerosol mass spectrometry", Int. J. Environ. Anal. Chem., 88 (3), 177-184 (2008)

B.J. Holmes and G.A. Petrucci, "Oligomerization of levoglucosan by Fenton chemistry in proxies of biomass burning aerosols", J. Atmos. Chem., 58, 151-166 (2007).

A.L. Hunt, G.A. Petrucci, P.R. Bierman and R.C. Finkel, "Investigation of metal matrix systems for cosmogenic 26Al analysis by accelerator mass spectrometry", Nucl. Instrum. Methods Phys. Res., Sect. B, 260, 633-636 (2007)

J. Zahardis and G.A Petrucci, "The oleic acid-ozone heterogeneous reaction system: products, kinetics, secondary chemistry, and atmospheric implications of a model system - a review", Atmos. Chem. Phys., 7, 1237-1274 (2007).

A.L. Hunt and G.A. Petrucci, "On-line organic aerosol analysis by mass spectrometry", Encyclopedia of Mass Spectrometry, Vol. 6, Elsevier (2006).

A.L. Hunt and G.A. Petrucci, "Photoelectron resonance capture ionization mass spectrometry (PERCI-MS)", Encyclopedia of Mass Spectrometry, Vol. 6, Elsevier (2006).

B.J. Holmes and G.A. Petrucci, "Water-soluble oligomer formation from acid catalyzed reactions of levoglucosan in proxies of atmospheric aqueous aerosols", Environ. Sci. Technol., 40 (11) 4983-4989, (2006).

J. Zahardis, B. W. LaFranchi and G.A. Petrucci, "Photoelectron Resonance Capture Ionization Mass Spectrometry of Fatty Acids in Olive Oil", Eur. J. Lipid Sci. Technol. 108 (11), 925-935,(2006).

B.W. LaFranchi and G.A. Petrucci, "A comprehensive characterization of photoelectron resonance capture ionization aerosol mass spectrometry for the quantitative and qualitative analysis of organic particulate matter," Int. J. Mass Spectrom., 258 (1-3), 120-133, (2006).

J. Zahardis, B.W. Lafranchi and G.A. Petrucci, "The heterogeneous reaction of particle-phase methyl esters and ozone elucidated by photoelectron resonance capture ionization: direct products of ozonolysis and secondary reactions leading to the formation of ketones", Int. J. Mass Spectrom. 253 38-47, (2006).

A.L. Hunt, G.A. Petrucci, P. Biermann and R.G. Finkel, "Metal matrices to optimize ion beam currents for accelerator mass spectrometry", Nucl. Instrum. Methods Phys. Res., Sect. B, 243, 216-222, (2006).

J. Zahardis, B.W. LaFranchi and G.A. Petrucci, "Direct Observation of Polymerization in the Oleic Acid-Ozone Heterogeneous Reaction System by Photoelectron Resonance Capture Ionization Aerosol Mass Spectrometry" Atmos. Environ. 40, 1661-1670, (2006)

Areas of Expertise and/or Research

analytical chemistry, mass spectrometry, environmental aerosols


  • Ph.D., University of Florida, Gainesville, FL, 1993
  • Postdoctoral fellowship, European Commission - Joint Research Center, Ispra, Italy 1993-1994


  • (802) 656-0957
Office Location:

Discovery W308