A5054330172- Mass Spectrometry Techniques and Applications
- Atmospheric chemistry and aerosols
- Isotope Analysis in Ecology
- Analytical Chemistry and Chromatography
- Advanced Chemical Sensor Technologies
- Air Quality and Health Impacts
- Indoor Air Quality and Microbial Exposure
- Metabolomics and Mass Spectrometry Studies
- Bacillus and Francisella bacterial research
- Air Quality Monitoring and Forecasting
- Hormonal and reproductive studies
- Advanced X-ray Imaging Techniques
- Inhalation and Respiratory Drug Delivery
- Radioactive contamination and transfer
- Nuclear Physics and Applications
- Catalytic Processes in Materials Science
- Atmospheric Ozone and Climate
- Chemical Thermodynamics and Molecular Structure
- X-ray Spectroscopy and Fluorescence Analysis
- Bacterial Identification and Susceptibility Testing
- Vehicle emissions and performance
- nanoparticles nucleation surface interactions
- Particle Accelerators and Free-Electron Lasers
- Lipid metabolism and biosynthesis
- Fermentation and Sensory Analysis
The University of Texas at Austin
2019-2020
Cornell University
1996-2020
Dell Children's Medical Center of Central Texas
2017-2018
Ithaca College
2018
Pediatrics and Genetics
2000-2014
SLAC National Accelerator Laboratory
2012
Deutsches Elektronen-Synchrotron DESY
2011-2012
Lawrence Livermore National Laboratory
2002-2011
University of Augsburg
2006
University of California, Davis
2003-2005
Diesel engines are known to emit high number concentrations of nanoparticles (diameter < 50 nm), but the physical and chemical mechanisms by which they form not understood. Information on composition is lacking because small size, low mass concentration, potential for contamination samples obtained standard techniques make difficult analyze. A nano-differential mobility analyzer was used size-select (mass median diameter ∼25−60 nm) from diesel engine exhaust subsequent analysis thermal...
Although high-precision isotope determinations are routine in many areas of natural science, the instrument principles for their measurements have remained remarkably unchanged four decades. The introduction continuous-flow techniques to ratio mass spectrometry (IRMS) instrumentation has precipitated a rapid expansion capabilities measurement C, N, O, S, and H isotopes 1990s. Elemental analyzers, based on flash combustion solid organic samples, interfaced IRMS facilitate C N isotopic...
Previous studies in our laboratory have shown that the major aerosol products formed gas-phase ozonolysis of 1-tetradecene presence excess alcohols, carboxylic acids, water vapor, and aldehydes are α-alkoxytridecyl, α-acyloxytridecyl, α-hydroxytridecyl hydroperoxides, secondary ozonides. These low volatility compounds from reactions C13 stabilized Criegee intermediates with acidic aldehydes. To obtain a more quantitative understanding chemical mechanism determine importance such atmosphere,...
The chemistry of secondary organic aerosol formation from reactions 1-tetradecene and O3 in dry air the presence excess alcohols carboxylic acids was investigated an environmental chamber using a thermal desorption particle beam mass spectrometer. Temperature-programmed collected shows that each reaction two major products are formed. more volatile compounds pair α-alkoxytridecyl or α-acyloxytridecyl hydroperoxides, which were identified by comparison spectra with those standard generated...
The rapid chemical analysis of individual cells is an analytical capability that will profoundly impact many fields including bioaerosol detection for biodefense and cellular diagnostics clinical medicine. This article describes a mass spectrometry-based technique the real-time reagentless characterization airborne without sample preparation. We characterize spectral signature Bacillus spores demonstrate ability to distinguish two spore species, B. thuringiensis atrophaeus, from one another...
An instrument has been developed for real-time, quantitative chemical analys is of organic particles in laboratory environments. In this apparatus, which we call a Thermal Desorption Particle Beam Mass Spectrometer (TDPBMS), are sampled into differentially-pumped vacuum chamber, focused narrow, low-divergence particle beam using aerodynamic lenses, and then transported high-vacuum region where they impact on heated surface, evaporate, the vapor mass analyzed quadrupole spectrometer. The...
Identification of organic compounds in multicomponent aerosols is demonstrated using temperature-programmed thermal desorption particle beam mass spectrometry. Aerosol particles are efficiently sampled into a high-vacuum chamber aerodynamic focusing techniques followed by impaction onto cold metal foil. The sample then slowly heated to achieve temporal separation components according their vapor pressures, while evaporating continuously mass-analyzed quadrupole spectrometer. Mass spectra the...
The chemical composition of secondary organic aerosol formed in an environmental chamber from ozonolysis 1-tetradecene humid and dry air was determined using a thermal desorption particle beam mass spectrometer (TDPBMS). major products are α-hydroxytridecyl hydroperoxide bis(α-hydroxytridecyl) peroxide symmetric C26 asymmetric C14 ozonides air. is by reaction stabilized Criegee biradicals with water vapor, the (a peroxyhemiacetal) subsequent tridecanal. reactions tridecanal formaldehyde....
Bioaerosol mass spectrometry is being developed to analyze and identify biological aerosols in real time. Characteristic spectra from individual bacterial endospores of Bacillus subtilis var. niger were obtained a bipolar aerosol time-of-flight spectrometer using pulsed 266-nm laser for molecular desorption ionization. Spectra single spores collected at an average fluence approximately 0.1 J/cm2 frequently contain prominent peaks attributed arginine, dipicolinic acid, glutamic but the...
ABSTRACT Single-particle laser desorption/ionization time-of-flight mass spectrometry, in the form of bioaerosol spectrometry (BAMS), was evaluated as a rapid detector for individual airborne, micron-sized, Mycobacterium tuberculosis H37Ra particles, comprised single cell or small number clumped cells. The BAMS spectral signatures aerosolized M. particles were found to be distinct from smegmatis , Bacillus atrophaeus and B. cereus using biomarker. This is first time potentially unique...
We report the first coupling of comprehensive two-dimensional gas chromatography (GC × GC) to online combustion isotope ratio mass spectrometry (C-IRMS). A GC system, equipped with a longitudinally modulated cryogenic system (LMCS), was interfaced an optimized low dead volume interface preserve <300 ms full width at half-maximum (fwhm) fast peaks generated on second column (GC2). The IRMS detector amplifiers were modified by configuration resistors and capacitors enable response, home-built...
We report the first demonstration of comprehensive two-dimensional gas chromatography combustion-isotope ratio mass spectrometry (GC×GCC-IRMS) for analysis urinary steroids to detect illicit synthetic testosterone use, interest in sport doping. GC coupled IRMS (GCC-IRMS) is currently used measure carbon isotope ratios (CIRs, δ(13)C) antidoping efforts; however, extensive cleanup urine extracts required prior enable baseline separation target steroids. With its greater capabilities, GC×GC has...
Different particulate matter (PM) samples were investigated by on-line single-particle aerosol time-of-flight mass spectrometry (ATOFMS). The consist of soot particulates made a diffusion flame generator (combustion standard, CAST), industrially produced material (printex), from diesel passenger car as well ambient (urban dust (NIST) and road tunnel dust). Five different CAST particle generated with elemental carbon (EC) organic (OC) content. reaerosolized analyzed ATOFMS, precipitated on...
Characterizing intense, focused x-ray free electron laser (FEL) pulses is crucial for their use in diffractive imaging.We describe how the distribution of average phase tilts and intensities on hard with peak 10 21 W/m 2 can be retrieved from an ensemble diffraction patterns produced by 70 nm-radius polystyrene spheres, a manner that mimics wavefront sensors.Besides showing adaptive geometric correction may necessary data randomly injected sample sources, our paper demonstrates possibility...
A temperature-programmed thermal desorption method for measuring vapor pressures of low-volatility organic aerosol compounds has been developed. The technique employs a particle beam mass spectrometer we have recently developed real-time composition analysis aerosols. Particles are size selected using differential mobility analyzer, sampled into high-vacuum chamber as an aerodynamically focused beam, collected by impaction on cryogenically cooled surface, slowly vaporized resistive heating,...
We have fully characterized the mass spectral signatures of individual Bacillus atrophaeus spores obtained using matrix-free laser desorption/ionization bioaerosol spectrometry (BAMS). Mass spectra grown in unlabeled, 13C-labeled, and 15N-labeled growth media were used to determine number carbon nitrogen atoms associated with each peak observed from positive negative ions. To parent ion structure fragment peaks, fragmentation patterns several chemical standards independently determined. Our...
Bioaerosol mass spectrometry is being developed to analyze and identify biological aerosols in real time. Mass spectra of individual Bacillus endospores were measured with a bipolar aerosol time-of-flight spectrometer which molecular desorption ionization produced using single laser pulse from Q-switched, frequency-quadrupled Nd:YAG that was modified have an approximately flattop profile. The flattened profile allowed the minimum fluence required desorb ionize significant numbers ions...
Single vegetative cells and spores of Bacillus atrophaeus, formerly subtilis var. niger, were analyzed using bioaerosol mass spectrometry. Key biomarkers identified from organisms grown in 13C 15N isotopically enriched media. Spore spectra contain peaks dicipolinate amino acids. The results indicate that compounds observed the correspond to material spore's core not exosporium. Standard mixtures for comparison. clearly different those spores, consisting mainly phosphate clusters acid fragments.
Monounsaturated normal fatty acids (n-MUFA) and saturated branched chain (BCFA) are structurally characterized by separate tandem mass spectrometry methods for double bond localization branching in their respective acid methyl ester (FAME) derivatives; however, these have never been applied to monounsaturated FAME. Here, we report application of electron ionization (EI)-MS/MS solvent-mediated covalent adduct chemical (CACI)-MS/MS BCFA esters (MUBCFAME) a length 15–20 carbons. A novel system...
On-line pyrolysis is described as an alternative to chemical means for reducing organic compounds hydrogen gas isotopic analysis by continuous-flow isotope ratio mass spectrometry. An empty ceramic tube, held at temperatures above 1000 °C, used in-line pyrolyze separated chromatography and followed a hydrogen-selective filter spectrometer purification measurement. Precision of light D/H measurement over several-fold signal intensity shown average SD <2‰ (δD), with corrections ion source...
Comprehensive 2‐dimensional gas chromatography (GC × GC), coupled to either a time of flight mass spectrometry (TOF‐MS) or fast scanning quadrupole MS (qMS) has greatly increased the peak capacity and separation space compared conventional GC‐MS. However, commercial GC GC‐TOFMS systems are not equipped with chemical ionization (CI) do provide dominant molecular ions enable single ion monitoring for maximal sensitivity. A GC‐qMS in mode was investigated electron (EI) positive CI (PCI), using...