Unusual collision-induced dissociation of fluorated and non-fluorated α-nitrotoluene analogs in a gas chromatograph triple-stage quadrupole mass spectrometer under electron-capturing negative-ion chemical ionization conditions

Abstract

Unusual collision-induced dissociation (CID) of perfluorated and non-perfluorated α -nitrotoluene analogs in a gas chromatograph triple-stage quadrupole (TSQ) mass spectrometer (GC–QqQ-MS) under electron-capturing negative-ion chemical ionization conditions is reported. CID of [M − 1] − of α-nitro-2,3,4,5,6-pentafluorotoluene (C 6F 5CH 2 NO 2) and α-nitro-2,5-difluorotoluene (C 6H 3F 2CH 2 NO 2) produced an intense ion with m/ z 66. By using 15N- or 18O-labelled C 6F 5CH 2 NO 2 analogs, we found that this anion has the formula C 3NO. By contrast, CID of [M − 1] − of α-nitrotoluene (C 6H 5CH 2 NO 2) and α-nitro-3,5-difluorotoluene (C 6H 3F 2CH 2 NO 2) produced an anion with m/ z 86 with the formula C 3H 4NO 2. The expected CID of the C N-bond of all α-nitrotoluene analogs to form the nitrite anion (NO 2 −, m/ z 46) did not occur. We propose mechanisms for the formation of the anions C 3NO and C 3H 4NO 2 in the collision chamber of the TSQ mass spectrometer. The most likely structures for the anion C 3NO are :C C C N O − and N C C C O −. The unique CID behavior of C 6F 5CH 2 NO 2 can be utilized to unequivocally identify and accurately quantify nitrite in biological fluids by GC–tandem MS.