Single Particle Mass Spectra Research Articles

Single-particle mass spectrometry of polystyrene microspheres and diamond nanocrystals.

High-resolution mass spectra of single submicrometer-sized particles are obtained using an electrospray ionization source in combination with an audio frequency quadrupole ion-trap mass spectrometer. Distinct from conventional methods, light scattering from a continuous Ar-ion laser is detected for particles ejected out of the ion trap. Typically, 10 particles are being trapped and interrogated in each measurement. With the audio frequency ion trap operated in a mass-selective instability mode, analysis of the particles reveals that they all differ in mass-to-charge ratio (m/z), and the individual peak in the observed mass spectrum is essentially derived from one single particle. A histogram of the spectra acquired in 10(2) repetitions of the experiment is equivalent to the single spectrum that would be observed when an ion ensemble of 10(3) particles is analyzed simultaneously using the single-particle mass spectrometer (SPMS). To calibrate such single-particle mass spectra, secular frequencies of the oscillatory motions of the individual particle within the trap are measured, and the trap parameter qz at the point of ejection is determined. A mass resolution exceeding 10(4) can readily be achieved in the absence of ion ensemble effect. We demonstrate in this work that the SPMS not only allows investigations of monodisperse polystyrene microspheres, but also is capable of detecting diamond nanoparticles with a nominal diameter of 100 nm, as well.

Relative sensitivity factors for alkali metal and ammonium cations in single-particle aerosol time-of-flight mass spectra.

A variety of factors have been investigated with regard to the quantitation of chemical species within individual ambient aerosol particles analyzed by laser desorption time-of-flight mass spectrometry. Spectrum to spectrum differences in the interaction of the particle with the ionization laser beam, which affect the absolute peak areas in the mass spectra, can be minimized by using relative peak areas instead of absolute peak areas in each spectrum. Whereas absolute peak areas vary by an average of 59% for a given ion peak in single particle mass spectra of a monodisperse aerosol of particles formed from the same solution, relative peak areas in the same mass spectra vary only by an average of 16%. Relative sensitivity factors (RSF) relating the mass spectral ion intensity of NH4+ and the alkali metal cations Li+, Na+, K+, Rb+, and Cs+ in single particle aerosol time-of-flight mass spectrometry to their bulk concentrations have been determined. The values for Li+/Na+, K+/Na+, Rb+/Na+, Cs+/Na+, and NH4+/Na+ are found to be 0.14, 5.1, 6.0, 7.9, and 0.014, respectively. The higher response for heavier cations of the alkali metals is consistent with the periodic trends of both ionization potential and lattice energies of the species of interest. The response factor for sodium and potassium cations has been used to accurately determine the relative amounts of Na+ and K+ in sea-salt particles, by analyzing a sample of approximately 360 ambient sea-salt particles. The relative amounts of Na+ and K+ are found to be 97 and 3% in particles, respectively, whereas in seawater they are, on average, 98 and 2%.

Real‐time single particle monitoring of a relative increase in marine aerosol concentration during winter rainstorms

During the months of December 1996 and January 1997, aerosol characterization was performed in real‐time at Riverside, CA, an inland location approximately 100 km east of the Los Angeles coast. Analysis was performed on a single particle basis with measurements of both particle size and composition. Data were collected throughout the course of five rainstorms. Single particle mass spectra demonstrate that obvious composition changes occur in the aerosol systems as the marine air mass is transported inland. While precipitation scavenging of aerosols was observed, there was a significant relative increase of sea salt particles in the non‐scavenged aerosol. Compositionally‐resolved particle size distributions also demonstrate real‐time changes that occur in the atmospheric aerosol sample.

Real-Time Monitoring of Pyrotechnically Derived Aerosol Particles in the Troposphere

Aerosol time-of-flight mass spectrometry (ATOFMS) allows for simultaneous determination of the aerodynamic particle size and chemical composition of individual particles in real time. Polydisperse particles originating from July 4, 1995, fireworks displays were monitored using ATOFMS over a 4-day period. Fireworks particles were identified by ion combinations in the single-particle mass spectra of potassium, aluminum, magnesium, barium, and lead and grouped into chemically specific categories. The relative number of ambient fireworks particles peaked on the morning of July 5, 1995, with representative particles being detected as late as July 19, 1995. The mass spectra of the detected particles are indicative of the original chemical composition of typical fireworks mixtures. This study demonstrates the ability of ATOFMS to serve as a real-time monitor of aerosols in the atmosphere, capable of detecting and tracking aerosol particles of a specific size and chemical composition from a particular source over time.

Thermo field dynamics and kinetic coefficients of a charged boson gas

Thermo field dynamics for inhomogeneous systems is generalized to quantum fields with a continuous single-particle mass spectrum. The modification of the hamiltonian in states with a local thermal Bogoliubov symmetry is used to calculate thermal conductivity and diffusion coefficient of pions interacting with hot, compressed nuclear matter.