Low-temperature plasma ionization-mass spectrometry for the analysis of compounds in organic aerosol particles.

Low-temperature plasma ionization, a technique that causes minimal fragmentation during ionization, is investigated as an ionization technique for mass spectrometric detection of the compounds in ambient organic aerosols in real time. The experiments presented in this paper demonstrate that ions are generated from compounds in the aerosol particles. The utility of this technique for detection of both positive and negative ions from the pyrolysate of multiple natural polymers is presented.

Contribution of organosulfur compounds to organic aerosol mass.

Organosulfates have been proposed as products of secondary organic aerosol formation. While organosulfates have been identified in ambient aerosol samples, a question remains as to the magnitude of their contribution to particulate organic mass. At the same time, discrepancies have been observed between total particulate sulfur measured by X-ray fluorescence (XRF) spectroscopy and sulfur present as inorganic sulfate measured by ion chromatography (IC) in fine particulate matter.

Laboratory and field evaluation of crystallized DOW 704 oil on the performance of the Well Impactor Ninety-Six fFine particulate matter fractionator.

Subsequent to the 1997 promulgation of the Federal Reference Method (FRM) for monitoring fine particulate matter (PM2.5) in ambient air, U.S.

The uptake of O3 by myristic acid-oleic acid mixed particles: evidence for solid surface layers.

The oleic acid ozonolysis in mixed oleic and myristic acid particles was studied in a flow tube reactor using single particle mass spectrometry. The change in reactivity was investigated as a function of the myristic acid concentration in these 2 micron particles. For pure oleic acid aerosol, the reactive ozone uptake coefficient, gamma, was found to be 3.

Cholesterol ozonolysis: kinetics, mechanism, and oligomer products.

Fine particles of cholesterol were reacted with ozone under pseudo-first-order conditions in an aerosol bag reactor. Gas-phase ozone was monitored using an ozone meter. Particle size distribution functions were determined using a scanning mobility particle sizer, which selected particle sizes for introduction into a photoionization aerosol mass spectrometer (PIAMS).

Reactive uptake of nitric acid onto sodium chloride aerosols across a wide range of relative humidities.

Reactive uptake coefficients for nitric acid onto size-selected (d(ve) = 102 and 233 nm) sodium chloride aerosols are determined for relative humidities (RH) between 85% and 10%. Both pure sodium chloride and sodium chloride mixed with magnesium chloride (X(Mg/Na) = 0.114, typical of sea salt) are studied.

Chemistry of particle inception and growth during alpha-pinene ozonolysis.

A flow-tube reactor was used to study the formation of particles from alpha-pinene ozonation. Particle phase products formed within the first 3-22 s of reaction were analyzed online using a scanning mobility particle sizer and two particle mass spectrometers. The first, a photoionization aerosol mass spectrometer (PIAMS), was used to determine the molecular composition of nascent particles between 30 and 50 nm in diameter.

Formation of oligomers in secondary organic aerosol.

The formation of oligomeric molecules, an important step in secondary organic aerosol production, is reported. Aerosols were produced by the reaction of alpha-pinene and ozone in the presence of acid seed aerosol and characterized by exact mass measurements and tandem mass spectrometry. Oligomeric products between 200 and 900 u were detected with both electrospray ionization and matrix-assisted laser desorption ionization.

On-line analysis of organic components in fine and ultrafine particles by photoionization aerosol mass spectrometry.

A new method, photoionization aerosol mass spectrometry (PIAMS), is described for real-time analysis of organic components in airborne particles below approximately 300 nm in diameter. Particles are focused through an aerodynamic lens assembly into the mass spectrometer where they are collected on a probe in the source region. After a sufficient amount of sample has been collected, the probe is irradiated with a pulsed infrared laser beam to vaporize organic components, which are then softly ionized with coherent vacuum ultraviolet radiation at 118 nm (10.

Mass spectrometry of individual particles between 50 and 750 nm in diameter at the Baltimore Supersite.

The performance of the real-time single-particle mass spectrometer RSMS III is evaluated for ambient fine and ultrafine particle number concentration measurements. The RSMS III couples aerodynamic size selection with laser ablation time-of-flight mass spectrometry for single-particle analysis. It was deployed at the Baltimore particulate matter Supersite for semi-continuous operation over an 8-month period.