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

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 (C6F5CH2NO2) and α-nitro-2,5-difluorotoluene (C6H3F2CH2NO2) produced an intense ion with m/z 66. By using 15N- or 18O-labelled C6F5CH2NO2 analogs, we found that this anion has the formula C3NO. By contrast, CID of [M − 1]− of α-nitrotoluene (C6H5CH2NO2) and α-nitro-3,5-difluorotoluene (C6H3F2CH2NO2) produced an anion with m/z 86 with the formula C3H4NO2. The expected CID of the CN-bond of all α-nitrotoluene analogs to form the nitrite anion (NO2−, m/z 46) did not occur. We propose mechanisms for the formation of the anions C3NO and C3H4NO2 in the collision chamber of the TSQ mass spectrometer. The most likely structures for the anion C3NO are :CCCNO− and NCCCO−. The unique CID behavior of C6F5CH2NO2 can be utilized to unequivocally identify and accurately quantify nitrite in biological fluids by GC-tandem MS.