In this Article, a compact Fourier transform ion cyclotron resonance (FTICR) mass spectrometer based on a permanent magnet is presented. This instrument has been developed for real-time analysis of gas emissions. The instrument is well-suited to industrial applications or analysis of toxic and complex samples where the concentrations can vary rapidly on a wide range. The novelty of this instrument is the ability to use either electron ionization (EI) or chemical ionization (CI) individually or both of them alternatively. Also in CI mode, different precursor ions can be used alternatively. Volatile organic compounds (VOCs) from the ppb level to very high concentrations (% level) can be detected by CI or EI. The magnet is composed of three Halbach arrays, and the nominal field achieved is 1.5 T. The ICR cell is a 3 cm side length cubic cell. The mass range is 12-200 u with a broad band detection. The mass accuracy of 0.005 u and the resolving power allow the separation of isobaric ions such as CH and CO. Gas introduction via controlled gas pulses, electron ionization, ion-molecule reactions, ion selection, and detection are all performed in the ICR cell. The potential of the instrument will be illustrated by an analysis of a gas mixture containing trace components at ppm level (VOCs) and components in the 0.5-100% range (N, alkanes, and CO).

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.

The volatile organic compounds emitted during polypropylene thermal oxidation at constant temperature were analyzed in real time using proton transfer reaction associated with Fourier transform ion cyclotron resonance mass spectrometry. Four major compounds were identified: acetone, formaldehyde, acetaldehyde, and methylacrolein. The time dependence of the emissions showed a complex profile consisting successively in an induction period, a stationary state with low emission rate, and final rapid degradation of the sample. The formaldehyde mixing ratio increases by a factor of 3 between the stationary state stage and the fast degradation stage, while the other products remain in constant proportions. The kinetic and mechanistic implications of these results are discussed.