Mechanism for Semiquinone Formation in the Oxygen Negative Chemical Ionization Mass Spectrometry of 2,3,7,8-Tetrachlorodibenzo-p-dioxin

Article abstract of DOI:10.1002/oms.1210190203

The high toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) has led to the development of selective and highly sensitive quantitative methods for mass spectral analysis.Analytical selectivity has been demonstrated for the oxygen negative chemical ionization (ONCI) reaction of TCDD in an oxygen-rich plasma.While the reaction product (4,5-dichloro-1,2-benzoquinone anion) of 2,3,7,8-TCDD and oxygen is well known, the mechanism of its formation has not been studied thoroughly.In this report the results of a study involving the reaction of (18)O2 with 2,3,7,8-TCDD under high pressure and low pressure ONCI conditions are reported.A mechanism is proposed which is compatible with the observation that one (18)O atom is incorporated into the product anion.