Real-time monitoring of low-mass ions by applying quadrupolar excitation to remeasurement in Fourier transform ion cyclotron resonance mass spectrometry

In the first application of quadrupolar excitation (QE) to the remeasuremen t of small ions, a remeasurement efficiency for benzene ions of 95% was ach ieved. The remeasurement experiment was optimized for excitation radius, st atic helium collisional cooling gas pressure and quadrupolar excitation amp litude. During initial studies conducted with benzene, it was found that ma intaining an ion excitation that utilizes 12% of the full cell radius minim izes the effects of the non-quadrupolar potential in a small cell. Optimiza tion of the benzene remeasurement experiment permits the real-time monitori ng of an ion-molecule reaction, specifically the broadband QE remeasurement of the self-chemical ionization of toluene, A single population of the ben zyl precursor ion is monitored for over 100 s as it reacts to produce xylyl ion. More than 30 min would be required to acquire the same quantity of da ta by the conventional methods in which a new ion population must be genera ted for each reaction time studied; this results in a 90% decrease in the a mount of time required to generate an ion-molecule reaction profile. This w ork demonstrates the first use of broadband QE remeasurement as a method fo r monitoring an entire low-mass, gas-phase ion-molecule reaction from a sin gle population of ions, Copyright (C) 2000 John Wiley & Sons, Ltd.