Lower stratosphere trace gas detection using aircraft-borne active chemical ionization mass spectrometry

Stratospheric Chemical Lifetime of Aviation Fuel Incomplete Combustion Products

The stratosphere contains haze rich in sulfuric acid, which plays a significant role in stratospheric chemistry and in global climate. Commercial aircraft deposit significant amounts of incomplete combustion products into the lower stratosphere. We have studied the stability of these incomplete combustion products to reaction with sulfuric acid, using a predictive model based on experimental reaction kinetics. We demonstrate that sulfuric acid chemistry is likely to be a significant component of the chemistry of organics in the stratosphere. We find that at least 25 of the 40 known incomplete combustion products from aviation fuel have lifetimes to reaction with aerosol sulfuric acid of at least months. We estimate that ~109 kg of long-lived products could be deposited per year in the lower stratosphere. We suggest that the high molecular weight organic compounds formed as incomplete combustion products of commercial long-haul aviation could play a significant role in the stratosphere.

Compact FTICR Mass Spectrometry for Real Time Monitoring of Volatile Organic Compounds

In this paper, we present a compact Fourier transform ion cyclotron resonance mass spectrometer (FTICR-MS) designed for real time analysis of volatile organic compounds (VOCs) in air or in water. The spectrometer is based on a structured permanent magnet made with NdFeB segments. Chemical ionization is implemented inside the ICR cell. The most widely used reaction is the proton transfer reaction using H₃O⁺ precursor ions, but other ionic precursors can be used to extend the range of species that can be detected. Complex mixtures are studied by switching automatically from one precursor to another. The accuracy obtained on the mass to charge ratio (Δm/z 5 × 10⁻³), allows a precise identification of the VOCs present and the limit of detection is 200 ppb without accumulation. The time resolution is a few seconds, mainly limited by the time necessary to come back to background pressure after the gas pulses. The real time measurement will be illustrated by the monitoring of VOCs produced during the thermal degradation of a polymer and by an example where three different precursor ions are used alternatively to monitor a gas sample.

Tandem mass spectrometry studies of acetone and acetone/water cluster ions

Ion clusters were formed in a temperature-variable high-pressure ion source from neat acetone and acetone/water mixtures and subjected to tandem mass spectrometry studies-unimolecular and collisionally activated mass-analyzed ion kinetic energy spectroscopy. The predominance of water loss from H(+)(H20)(A) l=3, where A = acetone, suggests that the solvation sphere around H3O(+) does not close at l = 3, contrary to the case of acetonitrile or dimethyl ether. The results may be interpreted in terms of suggested ion structures which involve isomerization enroute to dissociation. The virtual absence of H/D scrambling in the collisionally activated dissociation of H3O(+)(DA)3, DA =acetone-d 6, and of D3O(+)(A)3 means that if enolization takes place, it is a rate-determining step in an irreversible isomerization. The stability of H(+)(H2O)(A)3 is a dominant factor in the observation of acetone loss from H(+)(H20)(A)4.