NITRIC-OXIDE CHEMICAL-IONIZATION ION-TRAP MASS-SPECTROMETRY FOR THE DETERMINATION OF AUTOMOTIVE EXHAUST CONSTITUENTS

Nitric oxide chemical ionization in a glow discharge ionization source coupled with a quadrupole ion trap mass spectrometer has been evaluat ed for application to automotive exhaust measurements. Emphasis was pl aced on the determination of hydrocarbons at parts-per-million to part s-per-billion levels. Nitric oxide chemical ionization was found to yi eld diagnostic ions for alkanes, alkenes, and arenes, whereas water ch emical ionization failed to provide diagnostic ions for the alkanes, T he ability to measure a variety of hydrocarbons present at roughly 15 ppb at measurement rates of 3 Hz was demonstrated. All of the ions wit h potential to serve as parent ions in a tandem mass spectrometry expe riment were found to yield parent-to-product conversion efficiencies g reater than 75%. The flexibility afforded to the ion trap by the use o f tailored waveforms applied to the endcaps allows parallel monitoring schemes to be devised that provide many of the advantages of tandem m ass spectrometry without a major loss in measurement rate. A large los s in measurement rate would ordinarily result from the use of conventi onal tandem mass spectrometry experiments carried out in series for a large number of targeted components.