title: A distonic radical-ion for detection of traces of adventitious molecular oxygen (O2) in collision gases used in tandem mass spectrometers.
abstract: We describe a diagnostic ion that enables rapid semiquantitative evaluation of the degree of oxygen contamination in the collision gases used in tandem mass spectrometers. Upon collision-induced dissociation (CID), the m/z 359 positive ion generated from the analgesic etoricoxib undergoes a facile loss of a methyl sulfone radical [(•)SO(2)(CH(3)); 79-Da] to produce a distonic radical cation of m/z 280. The product-ion spectrum of this m/z 280 ion, recorded under low-energy activation on tandem-in-space QqQ or QqTof mass spectrometers using nitrogen from a generator as the collision gas, or tandem-in-time ion-trap (LCQ, LTQ) mass spectrometers using purified helium as the buffer gas, showed two unexpected peaks at m/z 312 and 295. This enigmatic m/z 312 ion, which bears a mass-to-charge ratio higher than that of the precursor ion, represented an addition of molecular oxygen (O(2)) to the precursor ion. The exceptional affinity of the m/z 280 radical cation towards oxygen was deployed to develop a method to determine the oxygen content in collision gases.
authors.affiliation: Center for Mass Spectrometry, Department of Chemistry, Chemical Biology and Biomedical Engineering, Stevens Institute of Technology, Hoboken, NJ, 07030, USA.
authors.forename: Freneil B
authors.initials: FB
authors.lastname: Jariwala
authors.forename: John A
authors.initials: JA
authors.lastname: Hibbs
authors.forename: Carl S
authors.initials: CS
authors.lastname: Weisbecker
authors.forename: John
authors.initials: J
authors.lastname: Ressler
authors.forename: Rahul L
authors.initials: RL
authors.lastname: Khade
authors.forename: Yong
authors.initials: Y
authors.lastname: Zhang
authors.forename: Athula B
authors.initials: AB
authors.lastname: Attygalle