Low-energy ionization of hydrocarbons in the quadrupole ion trap mass spectrometer

✍ Scribed by Stilianos G. Roussis; W. Patrick Fitzgerald; Andrew S. Cameron

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 274 KB
• Volume: 12
• Category: Article
• ISSN: 0951-4198
• DOI: 10.1002/(sici)1097-0231(19980415)12:7<373::aid-rcm168>3.0.co;2-5

✦ Synopsis

The capabilities of a commercial ion trap mass spectrometer to readily perform chemical ionization experiments have been exploited to account for the restrictions of the instrument to perform low-energy ($10 eV) electron ionization (EI) experiments. CS 2 and benzene have been used as representative reagent compounds for low-energy ionization by charge exchange in the ion trap with the main objective being the production of mass spectra of hydrocarbon compounds with intense peaks in the molecular ion region. n-Pentane was used as a representative small alkane reagent compound to investigate its capability to form intense peaks of molecular ion species in the spectra of saturated hydrocarbons. No intense peaks were produced in the molecular ion region, by any of the three reagents, for the mass spectra of model linear saturated hydrocarbons. The relatively weak stability of these compounds and the excess amounts of internal energy supplied by the various dynamic processes in the ion trap may partly account for the increased fragmentation. Intense molecular ion species and fragment ion peaks were observed in the mass spectra of cyclic saturated hydrocarbons. Charge exchange of aromatic compounds with CS 2 and benzene produced mass spectra with intense molecular ion peaks and limited fragmentation, similar to the mass spectra obtained in conventional mass spectrometers. The methods developed in this study were used for the analysis of typical middle distillate and heavy petroleum samples.