“…Therefore, separating toxic from non-toxic isomers is a major challenge that cannot be solved using GC alone, as witnessed by the coeluting isomers 2,3,7,8-TBDD (toxic) and 1,2,3,4-TBDD (less toxic) in Figure 5d. Fernando et al [103] showed that ion-molecule reactions with oxygen could be exploited to separate the coeluting isomers because 2,3,7,8-TBDD reacts with oxygen to produce the ether cleavage product C6H2BrO2 •− (m/z 265.840), whereas 1,2,3,4-TBDD cannot. When Structure-diagnostic reactions have also been observed in the positive ion mode 68 .…”